Gunnery  Department, 


BANCROFT  LIBRARY 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 


J.  Porter  Shaw  Collection 


Gift  of 
Marguerite  Bachrach 


INSPECTION 


AND 


PROOF   OF   CANNON. 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE. 
1864. 


BUREAU  OF  ORDNANCE,   Navy  Department,  March  23,  1864. 

SIR  :  The  Bureau  haa  the  honor  to  present  the  accompanying  rules  and  regulations  for 
the  "Inspection  and  Proof  of  Cannon"  for  the  Navy. 

These  have  been  carefully  compiled  and  revised  by  officers  most  experienced  in  ordnance, 
and  are  approved  by  the  Bureau.  It  therefore  respectfully  submits  them  for  the  adoption  of 
the  Navy  Department. 

I  am,  sir,  with  high  respect,  your  obedient  servant, 

H.  A.  WISE, 
Chief  of  Bureau  ad  interim. 
Honorable  GIDEON  WELLES, 

Secretary  of  the  Navy. 


NAVY  DEPARTMENT,    Washington,  March  30,  1864. 
SIR:  The  rules  and  regulations  for  the   "Inspection  and  Proof  of  Cannon,"   submitted 

with  your  letter  of  the  23d  instant,  are  hereby  approved,    and  all  officers  of  the  Navy  will 
strictly  observe  and  enforce  them. 

Very  respectfully, 

GIDEON  WELLES, 

Secretary  of  the  Navy. 
Commander  H.  A.  WISE, 

Chief  of  Bureau  of  Ordnance 

ad  interim,  Navy  Deparhment. 


A  2.^ 


INSPECTION  AND  PROOF  OF  CANNON, 


CONTRACTS. 

Contracts  for  guns  for  the  navy  shall  provide  for  the  uniformity  of  the  modo  of  their 
niiinufiicture,  as  well  as  of  the  metal  of  which  they  are  composed,  which  should  bo  of  the  best 
quality  attainable. 

To  this  end,  the  Chief  of  the  Bureau^of  Ordnance,  when  he  shall  deem  it  important,  may 
employ  some  competent  person  to  visit  the  furnaces  from  which  the  iron  is  to  be  supplied,  and 
examine  the  Various  ores  used,  for  the  purpose  of  selecting  the  fittest  kinds,  and  determining 
their  proper  treatment  for  making  gun-iron. 

Experience  having  shown  that  certain  kinds  of  metal  and  general  modes  of  treatment  are 
essential  to  the  production  of  guns  of  uniform  endurance,  these  conditions  will  be  insisted  on. 
But  as  it  is  also  desirable  to  obtain  the  experience  of  the  founder,  .he  will  be  the  jivlge  of  the 
particular  metal  and  details  of  treatment,  and  will  be  required  to  produce  a  satisfactory  trial-gun 
in  case  of  deviation  from  established  processes. 

.Before  proceeding  to  execute  a  contract,  a  trial-gun  may  therefore  be  ordered,  at  the  dis- 
cretion of  the  Bureau,  subject  to  the  supervision  of  the  resident  Inspector,  with  reference 
to  material  and  treatment,  and  to  be  exposed  to  extreme  proof  with  service  charges. 

After  undergoing  this  proof  in  a  manner  satisfactory  to  the  Bdreau,  the  trial-gun  will  servo 
aa  a  standard,  and  the  proportions  of  the  several  kinds  of  metal  used,  and  the  methods  employed 
in  its<nanufacture,  must  be  followed  in  all  respects  in  the  fabrication  of  the  other  guns. 

A  trial-gun  may  also  be  ordered  by  the  Bureau,  at  any  time  when  it  may  be  reasonably 
suspected  that  changes  have  occurred  in  the  quality  of  the  several  kinds  of  metal  usod  ;it  any 
foundry,  as  is  often  the  case  from  the  use  of  different  qualities  of  ores  from  the  same  bank,  or 
from  the  different  workings  of  the  same  furnace. 

But  whether  a  trial-gun  has  been  made  or  not,  a  gun  may  bo  selected  for  extreme  proof 
with  service  charges,  by  the  Chief  of  the  Bureau,  out  of  any  lot  of  guns  offered  under  contract, 
as  an  exponent  of  the  whole,  to  be  paid  for  by  the  Bureau  or  not,  as  may  be  stipulated  in  the 
contract. 


Contracts  for  guns  are  to  comprise  the  following  itetns,  subject  to  such  corrections  and 
additions  as  may  be  deemed  necessary,  from  time  to  time,  by  the  Bureau  of  Ordnance  : 

1st.  In  casting  any  particular  lot  of  guns,  iron  from  such  furnaces,  and  in  such  proportions 
of  each  grade  or  number;  of  pig,  and  such  fuel  is  to  be  used,  as  may  be  decided  on  at  the  time 
by  the  Bureau,  concurrently  with  the  founder. 

2d.  A  proper  proving  ground  is  to  be  provided,  and  a  suitable  "butt"  and  "bomb-proof 
shelter,"  when  requisite,  to  be  prepared  by  the  contractor,  and  to  be  so  situated  that  the 
firing  will  not  probably  be  interrupted  by  an  interference  of  the  authorities,  the  frequent 
passage  of  vehicles,  or  other  causes.  The  "butt"  is  to  be  so  constructed  as  to  allow  the  easy 
recovery  of  projectiles,  and  the  earth  in  it  to  be  free  from  rocks,  stones,  or  gravel ;  the  bomb- 
proof shelter  for  the  men  is  to  be  made  safe  and  convenient  of  access. 

3d.  Either  two  skids  or  a  ^proving  carriage  are  to  be  provided  by  the  contractor  for 
each  gun  to  be  fired.  If  skids  be  used,  they  are  to  be  of  sufficient  thickness  to  keep  the  bores 
of  the  guns  level  whilst  their  trunnions  rest  on  the  skids,  and  their  breeches  on  the  ground, 
and  of  such  length  that  the  guns  will  not  recoil  clear  of  them. 

4th.  The  ground  is  to  be  firm  enough  to  prevent  difficulty  in  transporting  and  handling 
the  guns.  The  guns  are  to  be  placed  on  the  ground,  at  the  expense  of  the  contractor,  who 
should  be  also  required  to  prevent  the  exposure  of  the  guns  to  the  weather,  and  to  have  them 
thoroughly  cleaned,  should  they  be  rusted,  before  prwof. 

5th.   The  labor  required  in  the  proof  will  be  paid  for  by  the  contractor. 

6th.  The  contractor  will  furnish  safe  storage  for  the  implements  used  in  proof  and  inspec- 
tion, without  charge.  The  storage  of  powder  and  projectiles,  and  the  transportation  of  them 
to  and  from  magazines,  for  the  proof  of  guns,  will  be  paid  for  by  the  Bureau.  odMi'*^  Vir«wdL»*- 

7th.  The  manufacture,  inspections,  and  proofs  of  all  the  guns  contracted  for,  are  to  con- 
form in  all  respects  to  the  conditions  prescribed  and  set  forth  in  the  specifications  and  drawings 
annexed  to  and  made  part  of  the  contract. 

8th.  The  contractor  is  to  afford  facilities  to  the  resident  Inspector  of  ordnance  for  the 
proper  discharge  of  the  duties  required  of  him  by  these  instructions,  and  by  the  specific 
instructions  given  to  him  from  time  to  time,  by  the  Chief  of  the  Bureau,  in  relation  to  the 
manufacture,  inspection,  and  proof  of  guns  and  projectiles. 

9th.  No  payment  is  to  be  made  to  contractors  for  guns  or  projectiles  until  they  shall 
be  delivered,  in  good  order,  at  the  place  designated  in  the  contract. 

"The  proving  carriage  is  a  simple  frame  of  oak,  with  cheeks  connected  by  transoms,  which  project  beyond  them  sufficiently 
for  the  handspikes  to  take.  It  has  trunnion  holes  and  cap-squares,  which  afford  the  means  of  proving  the  trunnions,  as  the 
carriage  is  intended  to  slide  on  the  ground.  It  presents  the  further  advantage  of  saving  much  labor,  as  does  the  pendulum 
in  extreme  proof.  When  a  proving  carriage  is  used,  some  means  are  required  readily  to  mount  and  dismount  the  guns. 
At  several  of  the  proving  grounds  permanent  skids  are  arranged  for  the  proof  of  cannon.  The  trunnions  rest  in  a  small  chock 
which  slides  on  two  of  the  skids,  the  breech  resting  on  a  third,  of  such  height  as  to  keep  the  gun  level.  They  are  placed  at 
an  inclination  of  about  eight  degrees,  and  the  gun  generally  returns  to  its  position  for  loading  after  each  fire. 


INSTRUCTIONS   TO  INSPECTORS    RESIDENT  AT  FOUNDRIES. 

L.The  Inspector  of  Ordnance,  resident  at  a  foundry  having  a  contract  with  or  order  from 
the  Bureau  of  Ordnance  for  the  manufacture  of  guns  or  projectiles,  is  expected  to  attend  daily, 
during  working  hours,  while  any  part  of  the  work  is  in  progress. 

2.  He  is  carefully  to  examine  and  note  the  kinds  and  qualities  of  the  several  lots  of  mate- 
rials, including  fuel,  collected  for  the  manufacture  of  guns  or  projectiles  for  the  public  service, 
and  to  familiarize  himself  with  the  various  processes  employed  in  making  guns  and  projectiles. 

3.  He  is  to  keep  a  journal  of  his  proceedings,  and  of  the  occurrences  at  the  foundry  or 
elsewhere  connected  with  the  \vork  in  hand,  noting  therein  every  circumstance  likely  to  be  of  use 
for  future  reference  and  guidance,  and  comprising  in  his  remarks  as  much  reliable  information 
as  is  attainable  upon  all  the  points  embraced  in  his  specific  instructions  from  the  Bureau  ;  and 
where,  in  any  case,  the  information  obtained  is  not  the  result  of  his  own  personal  observation, 
he  will  be  careful  to  note  the  source  from  which  it  is  derived. 

4.  He  will  also  keep  a  separate  and  minute  account  of  the  materials  and  manufacture  of  each 
gun,  in  reference  especially  to  the  points  to  which   his  attention  may  be  called  in  his  instruc- 
tions, but  also  comprising,  in  his  general  remarks,  every  point  which  may  suggest  itself  as  ira- N 
portant  for  reference. 

/  5.  He  will  see  that  each  of  the  several  kinds  of  metal  and  the  fuel  used  is  in  itself  of  uni- 
form quality,  and  bears  the  prescribed  proportion  to  the  whole  charge  of  the  furnace,  which 
[  charge  is  to  be  treated  alike  in  making  each  gun  contracted  for.  j 

6.  He  will  keep  a  careful  record,  in  the  prescribed  form,  of  the  manner  of  making  moulds, 
and  the  materials  used  in  making  them;  of  the  character  and  proportion  of  each  kind  and  quality 
of  metal  of  each  charge  of  the  furnace;  the  number  of  furnaces  used  ;  the  appearance  of  the 
fractures  of  the  pigs;  the  quantity  and  quality  of  the  fuel;  the  state  of  the  atmosphere;  the 
time  required  to  fuse  the  whole  charge,  and  the  time  it  is  kept  in  fusion  before  tapping;  the 
temperature  of  the  runners  and  of  the  mould ;  the  arrangements  for  and  the  time  occupied 
in  filling  the  mould;  the  mode  of  heating  the  pit  and  flask,  and  the  temperatures  thereof  at 
regular  intervals;  the  mode  and  the  time  occupied  in  cooling  the  casting;  the  temperature  of 
the  flask  when  hoisted  out  of  the  pit,  and  of  the  casting  when  taken  out  of  the  flask;  and 
every  other  particular  which  may  be  embraced  in  the  contract  or  in  his  instructions,, or  which 
may  present  itself  in  the  course  of  the  operations  and  tend  to  secure  uniformity  and  to  facili- 
tate comparison. 

This  record  should  also  embrace,  with  dates,  all  the  subsequent  operations  of  cutting,  turn- 
ing, boring,  chipping,  and  drilling,  and  the  tests  of  the  metal  afforded  by  each  of  these  pro- 
cesses as  to  toughness,  hardness,  soundness,  time  required,  color,  as  well  as  the  measurement, 
at  various  times,  the  tests  of  the  samples,  and  the  final  inspections  and  proofs;  a  copy  should 
be  left  with  the  foundry  for  future  reference. 

7.  He  is  expected,  also,  to  note  in  his  journal  any  particulars  relating  to  the  manufacture 
of  guus  or  projectiles  making  at  the  foundry  for  other  parties,  which  may  be  either  new  or  in 
nny  manner  suggestive  of  improvement. 


6 

He  will  keep  the  Bureau  advised  of  the  progress  of  the  work,  and  of  all  departures  from 
the  letter  or  spirit  of  the  contract;  and  will,  besides,  make  regular  reports,  on  the  last  day  of 
each  month,  of  what  has  been  done  in  the  course  of  it,  in  the  prescribed  form,  with  such  addi- 
tions as  circumstances  require. 

8.  He  will  make  timely  requisitions  on  the  Bureau  or  on  the  nearest,  navy  yard,  as  directed, 
subject  to  the  approval  of  the  Bureau,  for  such  ammunition  and  implements  as  may  be  required 
in  the  proof  of  the  guns  under  contract.     And  he  will  see  that  all  necessary  and  proper  arrange- 
ments are  made  on  the  proving  ground  in  due  season,  and  that  the  guns  are  properly  placed 
thereon  by  the  contractor:  and  will  notify  the  Bureau  when  everything  is  in  readiness  for  the 
final  inspection  and  proof,  in  order  that  there  may  be  no  delay  after  the  order  is  received  at  the 
foundry. 

9.  He  will  not  show  to  nor  leave  in  the  way  of  unauthorized  persons  any  plans  or  drawings, 
dimensions  of  guns,  or  the  guns  themselves,  or  any  information  respecting  proofs  or  experi- 
ments in  progress,   and  is  to  discourage   the   doing  so  by  the  contractors  or  their  agents. 
This  prohibition  to  form  part  of  the  contract  as  to  contractor. 

10.  As  soon  as  a  lot  of  guns  have  been  inspected  and  proved,  according  to  the  terms  of  the 
contract  and  the  instructions  of  the  Bureau  of  Ordnance,  the  Inspector  will  forward  his  reports 
thereon,  and  that  on  the  mechanical  tests  of  the  samples,  if  not  previously  sent,  to  the  Chief  of 
the  Bureau  for  his  decision.     In  his  records  and  reports  he  will  use  the  prescribed  forms. 

1 1.  Guns  are  not  to  be  received  nor  marked  except  with  the  Foundry  numbers  on  the  casca- 
bel,  nor  are  any  bills  for  them  to  be  approved  by  the  Inspector  until  he  shall  have  received  au- 
thority to  that  effect  from  the  Bureau. 

12.  A  certificate,  in  the  form  following,  is  always  to  accompany  the  bill  of  charges  for  ex- 
penses incurred  by  the  contractor  in  proving  guns,  viz  : 


r. 


FOUNDRY, 


'        / 


I  hereby  certify  that  the  alateriHjs    charged  In  the  foregoing  bill/nave  beenyused/and 
authorized  expenses  charged  therein  incurred,   it 
made  under  contact  with  the  Bureau  of  Onteance,  by 


the    aphorized  expenses  charged  therein  incUp/ed,   in  proving. — -/- \X   guns 


13.   The  bills  must  be  made  out  in  triplicate,  and  approved  by  the  Chief  of  the  Bureau, before 
they  can  be  paid  by  the  navy  agent. 

After  inspection,  the  bores  of  guns  are  to  be  oiled  with  fish  oil.     Oiling  the  outside  would 
prevent  their  being  readily  handled. 


FORM  OF  RECORD  TO  BE  KEPT  BY  THE  RESIDENT  INSPECTOR  AT  THE  FOUNDRY 

FOR  EACH  GUN  CAST. 


Calibre  and  datt, .     Foundry,  No.  — .      Weight  in  pound*. 


Date  i/7/i «  catt, 


Mrtal.  (Information  to  be  ob- 
tained in  relation  to  the 
furnace*,  ores,  anJ  fuel 
raed  in  smelting  must  he 
obtained  from  the  founder, 
unless  officers  are  gent  to 
the  furnaces.) 


From  what  ores,  and  the  situation  of  ore  beds. 
From  what  furnace  received. 
Kind  of  fuel  used  in  making  the  pig  iron. 
Cold,  hot,  or  warm  blast  used  in  milking  it. 

General  character  and  appearance  of  the  pig  iron,  as  respecta  color,  texture, 
and.  fracture. 


{Weight  of  different  kinds  of  pig  iron  used  from  different  ores  and  furnaces  for 
this  gun. 
Weight  used  of  different  fusions  of  each  kind  of  iron. 
Total  weight  of  metal  for  charge  of  furnace. 


Relating    to    the    process   of 
manufacture  and  cooling. 


Kind  of  furnace. 

Mode  of  preparing  the  hearth. 

How  many  furnaces  are  used  in  melting  iron  for  any  one  gun,  and  how  do 
their  streams  mingle  before  entering  the  mould. 

Kind  of  fuel  used. 

Mode  of  firing. 

Time  required  to  obtain  complete  fusion. 

Taking  out  specimens  during  the  progress  of  melting. 

Time  kept  in  fusion. 

How  introduced  into  the  mould  of  the  gun. 

What  precautions  are  taken  to  prevent  scoria  entering  the  trunnions. 

Time  employed  in  filling  the  mould. 

Dimensions  of  gun-head  and  nature  of  shrinkage 

Arrangements  for  retarding  the  cooling. 

Length  of  time  the  gun  is  left  in  pit  for  cooling.  ' 

Excess  in  the  diameter  in  any  part  of  the  casting  beyond  the  prescribed  dimen- 
sions of  the  gun. 

Temperature  of  mould,  (  at  the  time  of  casting,  and  after  being  opened,  and 

Temperature  of  pit,        )  when  the  gun  is  hoisted  out. 

Position  of  the  thermometer  in  the  pit. 

Temperature  of  the  pit,  and  of  the  external  air,  at  8  a.  m.  and  4  p.  m.  daily, 
during  the  time  the  gun  is  left  in  the  pit  for  cooling. 

Temperature  of  the  air,  and  gun  when  it  is  detached  from  the  mould. 

Under  the  head  of  general  remarks,  any  facts  which  may  seem  to  the  inspector 
worthy  of  record. 


8 


Qualities  of  the  metal. 


External  imperfections,  if  any,  of  the  gun  when  cleaned. 
How  does  the  metal  work  under  the  tools,  hard,  soft,  or  otherwise  ? 
Is  it  tenacious  or  brittle  ? 
Time  occupied  in  boring  the  gun. 
Time  occupied  in  turning  the  gun. 
Appearance  of  the  bore,  perfect  or  otherwise. 
Appearance  of  surface  after  being  brought  down  to  true  dimensions. 
Appearance  of  core,  sound  or  otherwise. 
Appearance  of  core-metal  at  places  of  fracture. 
Tenacity  and  density  of  specimens  from  gun-heads. 

Tenacity  and  density  of  specimens  from  core  taken  between  muzzle  and  trun- 
nions. 

Tenacity  and  density  of  specimens  from  nearly  opposite  to  trunnions. 
Tenacity  and  density  of  specimens  from  near  the  bottom  of  bore. 
Any  apparent  causes  for  doubting  the  good  qualities  and. strength  of  the  gun. 
Any  other  useful  information. 


The  Resident  Inspector  shall  take  accurate  measurements  of  the  different  parts  of  the  guns 
as  soon  as  they  are  finished.  These  examinations  are  for  the  information  of  all  the  parties,  but 
are  not  to  be  considered  as  decisive  for  reception. 

As  soon  as  the  casting  has  been  completed  the  information  shall  be  collected  and  forwarded 
to  the  Bureau  of  Ordnance,  according  to  the  form  now  in  use,  or  that  which  shall  be  from 
time  to  time  prescribed. 

The  manufacture  of  rifled  cannon  and  projectiles  being  consided  as  yet  only  experimental, 
specific  directions  relative  to  their  manufacture,  inspection,  and  proof,  will  be  given  from 
time  to  time  as  requisite. 


9 


TENACITY   AND   DENSITY   OF  IRON. 

The  Resident  Inspecting  Officer  will  subject  the  metal  of  each  gun  to  the  usual  tests  of  tena- 
city and  density,  and  for  this  purpose  will  take  samples  from  the  sinking  head,  the  core,  or 
such  other  available  parts  of  the  casting,  and  in  such  manner  as  may  be  prescribed,  and  will 
forward  duplicate  specimens  to  the  Ordnance  Yard  at  Washington  for  trial. 

The  axis  of  the  sample  is  to  be  parallel  to  or  at  right  angles  with  the  axis  of  the  casting,  aa 
may  be  required  by  the  Bureau.  Fairly  to  represent  the  metal  of  the  gun,  the  samples  from 
the  head  should  not  be  taken  from  the  part  opposite  the  bore,  but  opposite  to  the  middle  of 
the  thickness  of  the  metal  remaining  in  the  gun  after  being  bored  and  turned.  The  mass  from 
which  the  sample  is  taken,  whether  sinking  head  or  core,  must  have  the  same  foundry  number 
cast  or  stamped  upon  it  as  the  gun  to  which  it  belongs,  before  being  taken  away  from  the 
gun.  Each  sample  must  have  the  foundry  number  of  the  casting  it  represents  ;  and  an  initial 
letter  and  a  number,  designating  the  part  of  the  gun  or  gun-head  from  which  it  was  taken, 
and  its  distance  from  the  axis  of  the  bore,  and  from  the  base  line,  stamped  upon  both  its  ends. 
To  prevent  confusion,  the  samples  should  be  marked  on  one  end  before  they  are  disconnected 
from  the  mass,  and  should  not  be  separated  from  it,  except  in  the  presence  of  the  inspecting 
officer. 

When  practicable,  the  tests  are  to  be  made  at  the  foundry,  before  the  guns  are  subjected 
to  proof.  They  are  to  be  carefully  made,  and  duly  recorded  and  reported  to  the  Bureau  with 
the  other  proofs  and  inspections,  that  they  may  afford  means  of  comparison  between  the  metal 
of  different  foundries  and  guns. 

No  particular  value  is  attached  to  these  tests  as  an  indication  of  the  endurance  of  the  gun, 
but  only  as  exhibiting  the  similarity  that  the  several  guns  bear  to  the  standard  gun.  Experi- 
ence has  shown  that  a  variation  of  2,250  pounds,  more  or  less,  in  the  tensile  strength,  is  a 
sufficient  limit  to  be  allowed,  and  within  which  to  confine  the  founders;  an  exact  adherence 
being  impossible. 

THE  INSTRUMENTS  employed  in  TESTING  METALS  are  as  follows  : 

THE  TESTING  MACHINE,  (devised  by  Major  W.  Wade,)  complete  with  the  implements  for 
determining  the  resistance  offered  by  various  kinds  of  metal  to  tensile,  torsional,  transverse, 
bursting,  crushing,  and  indenting  forces. 

THE  HYDROMETER,  (constructed  on  the  principle  of  Nicholson's,  and  improved  by  Wade,) 
complete  with  implements  and  adjusting  weight  for  the  determination  of  the  density  of  samples.* 

The  elaborate  "Reports  of  Experiments  on  the  Strength  and  other  Properties  of  Metal  for 
Cannon,"  published  in  1856,  by  authority  of  the  Secretary  of  War,  contains  full  descriptions 
of  these  instruments,  and  their  implements,  with  plates.  A  copy  of  this  work  will  be  furnished 
for  the  use  of  the  inspecting  officer  at  each  of  the  foundries. 

WURDEMAN'S  DENSIMETER,  or  balance  for  specific  gravities. 
2 


10 


DETERMINATION  OF  DENSITY  AND  TENACITY. 

DENSITY. 

To  determine  the  density,  the  sample  is  weighed  in  air,  and  in  pure  distilled  water.  Clear 
rain  or  river  water  may  he  substituted,  if  its  relative  density  be  first  accurately  determined. 
The  hydrometer  may  be  employed  for  this  purpose,  and  the  proper  correction  applied. 

The  weight  of  the  hydrometer,  together  with  its  balance  weight  in  distilled  water,  deter- 
mines the  weight  of  a  quantity  of  standard  water  equal  in  bulk  to  the  immersed  part  of  the 
instrument. 

The  weight  of  the  hydrometer  and  its  load,  when  immersed  in  like  manner,  in  any  other 
water  at  the  same  temperature,  determines  the  weight  of  a  corresponding  bulk  of  the  latter  ; 
and  this  weight,  divided  by  the  former,  gives  the  multiplier  for  correcting  the  density,  when 
ascertained  in  any  other  than  distilled  water. 

At  the  foundries,  generally,  river  water  is  found  to  be  sufficiently  pure  for  use,  without 
requiring  any  correction. 

In  determining  the  density  of  samples,  first  load  the  weight-dish  with  the  grain  weights, 
until  the  hydrometer  is  immersed  to  its  zero  mark,  and  then  record  the  sum  of  the  w'eights  in 
the  dish  as  the  balance  of  the  hydrometer.  Next  remove  the  weights,  and  place  the  sample  in  the . 
dish  with  as  many  weights  as  will  bring  the  hydrometer  again  to  its  zero  point,  and  record  the 
sum  of  these  weights  as  the  balance  with  the  sample  in  air.  The  difference  between  these 
balances  is  the  weight  of  the  sample  in  air.  Then  place  the  sample  on  the  bulb,  and  immerse 
both,  until  the  hydrometer  is  again  adjusted  to  its  zero,  and  then  record  the  weights  employed 
in  this  adjustment  as  the  balance  with  the  sample  in  water.  The  difference  between  this  balance 
and  that  given  by  the  sample  in  air  is  the  weight  of  water  displaced  by  the  immersed  sample. 
lu  this  operation,  care  must  be  taken  to  remove  any  air  bubbles,  which  is  facilitated  by  first 
wetting  the  specimen. 

The  temperature  of  the  water  at  the  time  of  weighing  the  immersed  sample  is  observed 
and  noted  by  means  of  a  thermometer  suspended  in  it.  If  it  is  not  at  60°,  the  weight  of  water 
displaced  by  the  sample  is  divided  by  the  tabular  number  opposite  the  noted  temperature, 
and  the  quotient  gives  the  corrected  displacement.  The  weight  of  the  sample  in  air,  divided 
by  the  corrected  displacement,  gives  the  density  of  the  sample. 


EXAMPLE. 


Sample  No.  4  H,  from  gun  head  : 

Balance  of  the  hydrometer 11485.0 

Balance  with  sample  in  air 923.0 


Difference  =  weight  of  sample  in  air 10562.0 


11 

Balance  with  sample  in  water 2370.4 

Balance  with  sample  in  air 923.0 


Difference  =  weight  of  water  displaced :  noted  temperature,  72  J° 1447.4 

Tabular  number  72  J=  .998912 
Then     1447.4 

=  1449.0  =  corrected  displacement 

.998912 
And      10562 

=7.289  =  density. 

1449 

Or  by  logarithms : 

Logarithm*. 

Water  displaced  at  72J°  =  1447.4 3.1C05886 

Tabular  number  for  72J°  =  .998912 I  9995274 


Logarithm  of  corrected  displacement 3.1610612 

Weight  of  sample  in  air=  10562 4.0237461 

Corrected  displacement 3.1610612 


Density  =  7.289  = 0.8626849 

If  impure  water  has  been  used,  correct  the  ascertained  density  by  the  rule  given  in  the 
last  paragraph. 

The  determination  of  densities  by  the  hydrometer,  (or  hydrostatic  balance,)  although 
theoretically  exact,  requires  much  practice  to  arrive  at  correct  results,  and  is  moreover  very 
tedious. 

The  densimeter,  or  balance,  may  therefore  be  advantageously  substituted  for  it,  the  results 
being  occasionally  checked  by  the  hydrometer. 


12 

Weights  of  distilled  water  displaced  ly  the  same  glass  bulb  at  different  temperatures,    compiled  by  W.  Wade  from  Uasslcr'i 

report  on  weights  and  measures. 


Tempera- 
ture, Fahr. 

Weight  of  water 
reduced  to  an  unit. 

Logarithms  of 
weights. 

Tempera- 
ture, Fahr. 

Weight  of  water 
reduced  to  an  unit. 

Logarithms  of 
weights. 

Tempera- 
ture, Fahr. 

Weight  of  water 
reduced  to  an  unit. 

Logarithms  of 
weights. 

o 

o 

o 

32.00 

1.  000395 

0.  0001706 

45.  00 

1.  000621 

0.  0002699 

58.00 

1.000133 

0.  0000579 

.25 

406 

.  0001764 

.25 

619 

.  0002687 

.25 

118 

.  0000512 

.50 

420 

.0001825 

.50 

616 

.  0002675 

.50 

101 

.  0000439 

.75 

433 

.0001880 

.75 

613 

.  0002660 

.75 

085 

.0000368 

33.00 

444 

.  0001928 

46.00 

610 

.0002646 

59.00 

068 

.  0000296 

.25 

455 

.  0001975 

.25 

606 

.  0002631 

.25 

051 

.0000222 

.50 

467 

.  0002028 

.50 

602 

.0002615 

.50 

034 

.  0000149 

.75 

479 

.0002078 

.75 

598 

.  0002598 

.75 

017 

.  0000072 

34.00 

489 

.  0002123 

47.00 

594 

.  0002578 

60.00 

1.000000 

0.  0000000 

.25 

499 

.0002167 

.25 

589 

.  0002558 

.25 

0.  999981 

1.9999919 

.50 

510 

.  0002214 

.50 

584 

.  0002537 

.50 

963 

.9999839 

.75 

519 

.  0002253 

.75 

579 

.  0002515 

.75 

945 

.9999760 

35.00 

527 

.  0002288 

48.00 

574 

.  0002493 

61.00 

927 

.9999681 

.25 

536 

.  0002329 

.25 

569 

.  0002470 

.25 

909 

.9999603 

.50 

545 

.  0002366 

.50 

564 

.  0002448 

.50 

890 

.9999522 

.75 

553 

.  0002401 

.75 

558 

.  0002421 

.75 

871 

.9999440 

36.00 

560 

.  0002432 

49.00 

551 

.0002393 

62.00 

853 

.9999361 

.25 

566 

.  0002459 

.25 

545 

.  0002366 

.25 

834 

.  9999280 

.50 

572 

.  0002463 

.50 

538 

.0002336 

.50 

814 

.9999193 

.75 

577 

.  0002504 

.75 

531 

.  0002306 

.75 

795 

.  9999108 

37.00 

581 

.  0002523 

50.00 

524 

.  0002276 

63.00 

774 

.9999020 

.25 

586 

.  0002542 

.25 

517 

.  0002244 

.25 

753 

.  9998929 

.50 

589 

.  0002561 

.50 

508 

.0002207 

.50 

733 

.  9998840 

.75 

595 

.  0002581 

.75 

499 

.  0002168 

.75 

712 

.  9998747 

38.00 

599 

.  0002603 

51.00 

490 

.  0002130 

64.00 

692 

.9998660 

.25 

604 

.  0002622 

.25 

482 

.  0002191 

.25 

672 

.  9998574 

.50 

609 

.0002642 

.50 

472 

.  0002050 

.50 

651 

.  9998483 

.75 

614 

.0002666 

.75 

462 

.  0002007 

.75 

629 

.  9998388 

39.00 

619 

.  0002685 

52.00 

452 

.  0001961 

65.00 

608 

.9998294 

.25 

628 

.  0002725 

.25 

441 

.  0001915 

.25 

585 

.9998198 

.50. 

635 

.0002755 

.50 

430 

.  0001869 

.50 

563 

.9998104 

.75 

642 

.0002786 

.75 

419 

.  0001821 

.75 

542 

.9998011 

40.00 

646 

.  0002806 

53.00 

409 

.  0001775 

66.00 

521 

.  9997918 

.25 

649 

.  0002817 

.25 

398 

.  0001727 

.25 

499 

.9997822 

.50 

650 

.  0002821 

.50 

387 

.  0001679 

.50 

479 

.9997737 

.75 

650 

.  0002821 

.75 

374 

.  0001625 

.75 

454 

.9997630 

41.00 

649 

.  0002819 

54.00 

363 

.  0001574 

67.00 

432 

.9997533 

.25 

649 

.  0002815 

.25 

349 

.  0001515 

.25 

409 

.9997435 

.50 

647 

.  0002810 

.50 

337 

.  0001465 

.50 

387 

.  9997338 

.75 

645 

.0002802 

.75 

322 

.0001398 

.75 

365 

.9997243 

42.00 

644 

.0002796 

55.00 

307 

.0001348 

68.00 

343 

.9997146 

.25 

643 

.0002792 

.25 

296 

.  0001286 

.25 

320 

.  9997047 

.50 

642 

.0002787 

.50 

282 

.  0001223 

.50 

297 

.9996945 

.75 

641 

.0002781 

.75 

267 

.  0001161 

.75 

273 

.9996843 

43.00 

639 

.  0002774 

56.00 

254 

.  0001103 

69.00 

249 

.9996740 

.25 

637 

.0002766 

.25 

239 

.  0001040 

.25 

226 

.9996636 

.50 

ea5 

.  0002756 

.50 

224 

.  0000973 

.50 

202 

.9996532 

.75 

633 

.  0002748 

.75 

209 

.  0000910 

.75 

178 

.9996427 

44.00 

631 

.  0002740 

57.00 

195 

.  0000846 

70.00 

153 

.  9996320 

.25 

629 

.0002731 

.25 

181 

.  0000783 

.25 

127 

.  9996208 

.50 

626 

.  0002721 

.50 

165 

.  0000717 

.50 

102 

.9996098 

.75 

1.000624 

0.  0002710 

.75 

1.000148 

0.  0000644 

.75 

0.999076 

T.  9995985 

13 


of  diitilltd  trattr  diiplaetd  by  the  lamt  glati  knit  at  diftreut  temptraturti,  l(c.— Continued. 


b 

Weight  of  wa- 
ter reduced 
to  an  unit. 

}! 

Temperature, 
Fahr. 

Weipht  of  wa- 
ter reduced 
to  an  unit 

•o 

1* 

f  * 

Temperature, 
Fahr. 

Weipht  of  wa- 
ter reduced 
to  an  unit. 

"3 

Is 

It 
J 

o 

o 

o 

71.00 

0.999050 

1.9995873 

76.25 

0.998430 

~1.  9993175 

81.50 

0.997754 

"1.9990233 

.as 

024 

.9995759 

.50 

399 

.9993039 

.75 

718 

.9990079 

.50 

0.986907 

.9995648 

.75 

367 

.9992904 

82.00 

681 

.9989918 

.75 

969 

.9996588 

77.00 

337 

.9992771 

.85 

644 

.9989756 

78.00 

942 

.9995401 

.85 

309 

.9992649 

.50 

607 

.9989596 

.35 

912 

.9995274 

.50 

278 

.9992515 

.75 

571 

JBKM:!.* 

.50 

884 

.9995150 

.75 

848 

.9992382 

83.00 

536 

.9989286 

.75 

855 

.9996027 

78.00 

216 

.9992244 

.85 

500 

.9989138 

73.00 

-•.'.-. 

.9994892 

.85 

184 

.9992104 

.50 

468 

.9988969 

.85 

795 

.9994765 

.50 

152 

.9991965 

.76 

433 

.9988837 

.50 

766 

.9994635 

.75 

120 

.9991836 

-4.  IN' 

398 

.9988684 

.75 

736 

.9994506 

79.00 

088 

.9991686 

.25 

363 

.9988532 

74.00 

705 

.9994373 

.25 

055 

.9991545 

.50 

327 

.9988378 

.85 

675 

.9994241 

.50 

022 

.9991400 

.75 

292 

.9988223 

.50 

645 

.9994113 

.75 

0.997989 

.9991258 

85.00 

256 

.9988068 

.75 

615 

.9993979 

80.00 

956 

.9991113 

.25 

220 

.9987908 

75.00 

584 

.9993845 

.25 

923 

.9990970 

.50 

183 

.9987750 

.85 

553 

.9993710 

.50 

889 

.9990822 

.75 

150 

.9987604 

.50 

521 

.9993574 

.75 

855 

.9990673 

86.00 

0.997116 

1.9987456 

.75 

492 

.9993440 

81.00 

821 

.9990526 

76.00 

0.996461 

1.9993313 

.25 

0.997788 

1.9990383 

To  make  the  corrections  for  the  weight  of  water  displaced  when  the  body  is  weighed  at  any 
other  temperature  than  (TO0,  divide  the  ascertained  displacement  by  that  number  in  the  table 
which  corresponds  with  the  noted  temperature,  and  the  quotient  will  be  the  weight  of  water 
which  the  same  body  would  have  displaced  in  the  same  water  if  weighed  at  the  temperature 
of  60°.  Or  by  logarithms,  subtract  the  logarithm  opposite  the  noted  temperature  from  the 
ascertained  logarithm  of  displacement,  and  the  remainder  will  be  the  logarithm  of  the  corrected 
displacement.  The  volume  of  the  body  weighed  changes  with  variations  of  temperature,  and 
this  will  cause  a  slight  error  when  the  weighings  are  made  at  extremes  of  temperature.  But 
as  the  difference  between  the  dilatation  by  heat  of  the  glass  bulb  and  cast-iron  cannot  bo 
measured,  error  from  this  cause  may  be  neglected. 

The  temperature  of  60°  Fahrenheit  has  been  taken  as  the  nnit,  because  that  is  about  the 
medium  temperature  which  occurs  in  ordinary  practice. 


14 

WURDEMAN'S  DENSIMETER,  OR  BALANCE  FOR  SPECIFIC  GRAVITIES. 

DESCRIPTION. 

The  balance  for  the  determination  of  specific  gravities  is  in  principle  a  simple  beam 
scale  of  accurate  workmanship. 

As  made  by  Wurdeman,  it  consists  of  an  open  beam  of  German  silver,  twelve  and  nine 
tenths  (12^,)  inches  in  length  between  the  knife  edges;  one  and  three  fourths  (1|)  inches  in 
width  at  the  centre;  three  fourths  (|)  of  an  inch  at  the  extremities  of  the  beam;  and  two 
tenths  (T20)  of  an  inch  in  thickness. 

From  the  extremities  of  the  beam  the  scale  pans  are  suspended  on  knife  edges. 

The  knife  edge,  in  the  centre  of  the  beam,  is  one  and  four  tenths  (!T*o)  inches  long;  those 
at  the  extremities  nine  tenths  (y9,)  of  an  inch;  all  bearing  their  lengths  on  steel  plates,  which 
are  preferable  to  stones,  as  the  latter  are  seldom  of  sufficient  uniformity  in  texture  to  give,  in 
cutting  and  polishing  a  perfectly' plain  surface. 

The  beam  is  supported  on  a  hollow  column,  through  which  a  rod  passes  for  lifting  the  beam, 
which,  when  not  in  use,  rests  on  its  Y's  on  a  cross-bar  at  the  top  of  the  column;  this  bar  also 
supports  the  scale  pans  on  separate  rests,  free  from  contact  with  the  knife  edges. 

The  column  is  set  on  a  brass  plate,  furnished  with  a  circular  spirit  level  and  foot  screws 
for  accurately  levelling  it. 

The  whole  apparatus  is  enclosed  in  a  glass  case,  to  protect  it  from  dust  or  currents  of  air, 
with  a  sliding  front,  which  is  counterpoised  for  convenient  manipulation. 

ADJUSTMENTS. 

The  beam  is  balanced  by  two  adjustments  placed  above  it:  Firstly,  by  the  horizontal 
screws,  with  milled  heads,  for  the  zero  of  the  index  below;  and,  secondly,  by  the  large  nut  on 
the  perpendicular  screw  for  vertical  balance.  This  last,  when  once  set,  it  is  seldom  necessary 
to  touch. 

To  adjust  the  arms  to  equal  length:  There  is  to  each  knife-edge  end  a  steel  screw,  with 
<C~  capstan  head,  which,  when  screwed  forward,  will  spring  out  the  part  on  which  the  knife  edge 
rests,  and  thus  lengthen  its  distance  from  the  centre.  Both  ends  are  made  thus  adjustable,  by 
which  means  perfect  symmetry  of  the  two  parts  of  the  beam  is  obtained,  and  the  necessity  of 
screwing  back  during  the  adjustment  is  obviated,  since  it  will  merely  be  necessary  to  lengthen 
the  arm  which  proves  to  be  shortest. 

To  test  this,  the  relative  place  of  the  scales  should  be  changed  after  first  balancing  them 
exactly;  if,  after  the  change,  either  preponderates,  it  proves  that  arm  to  be  the  longest.  One 
half  the  difference  is  to  be  corrected  with  weights,  and  the  other  half  with  the  adjusting  screws. 
Great  caution  must,  however,  be  observed  in  not  screwing  up  too  much  at  a  time. 

A  correct  result  in  weighing  may  be  obtained  without  this  adjustment  being  absolutely 
exact,  by  first  balancing  the  specimen  to  be  weighed  with  any  convenient  substance,  then  re- 
moving the  specimen  and  substituting  in  its  place  known  weights  until  equilibrium  with  the 
counterpoise  is  restored. 


15 

/  USE  OP  THE  INSTRUMENT. 

By  a  crank  placed  in  front  of  the  case,  the  centre  bearing  is  gently  raised,  which,  lifting 
the  beam  off  its  Y's,  also  takes  up  the  scales. 

When  the  beam  is  completely  raised,  the  oscillations  of  the  scales  are  arrested  by  touching 
the  spring  lever  on  the  right  of  the  crank.  On  abandoning  the  lever  the  preponderance  of 
the  specimen,  or  the  weight,  will  immediately  be  manifested,  and  additional  weights  may  be 
added  or  removed  until  they  are  in  equilibrium. 

When  placing  the  specimen  and  estimated  counterbalancing  weights  in  the  scales,  the  beam 
should  always  be  let  down  on  the  supports;  but  small  weights  may  be  added  or  changed  whilst 
simply  arresting  the  scales  with  the  lever. 

The  door  should  not  be  pushed  up  higher  than  is  just  necessary  to  obtain  convenient  access. 

As  the  balance  is  very  sensitive,  care  should  be  taken  not  to  abrade  the  pans  by  carelessly 
putting  in  the  specimens,  or  rubbing  to  remove  dust.  . 

DETERMINATION  OF   SPECIFIC   GRAVITY.     ^ 

For  the  determination  of  specific  gravities  a  German  silver  vessel  is  used,  just  large  enough 
to  conveniently  hold  the  specimen,  and  open  at  the  top,  which  is  planed  off  perfectly  straight, 
so  that  a  plate-glass,  provided  for  the  purpose,  can  be  slid  over  it,  and  will  shut  air-tight. 
This  vessel  is  filled  with  distilled  water,  carefully  removing  air  bubbles  from  inside  the  vessel, 
or  drops  mechanically  adhering  to  the  outside.  Weight  and  temperature  are  noted,  and  a 
table  may  be  computed,  so  that  this  element  constitutes,  for  the  instrument  used,  a  constant. 
It  will  be  convenient  to  keep  the  water  in  a  reservoir  of  considerable  size,  to  avoid  the  incon- 
venience of  frequent  changes  of  temperature. 

The  absolute  weight  of  the  specimen  having  been  previously  taken  and  noted,  the  specimen 
is  then  submerged  in  the  vessel,  and  displaces  a  quantity  of  water  equal  to  its  volume.  The 
vessel  is  again  covered  with  the  plate-glass,  using  the  same  precautions  as  above,  and  the 
weight  is  taken. 

Since  specific  gravity  is  represented  by  the  ratio  of  the  absolute  weights  of  the  same 
volume  of  water,  and  of  the  article  to  be  determined,  we  have  to  divide  the  weight  of  specimen 
by  a  quantity  obtained,  by  deducting  the  weight  of  the  vessel,  with  specimen  inserted,  from 
the  sum  of  weight  of  vessel  filled  with  water,  aud  of  the  weight  of  specimen. 

Therefore,  if 

0    =  Weight  of  vessel  filled  with  water  (constant); 
W  =  Absolute  weight  of  specimen; 
Wi  =  Weight  of  vessel  with  specimen  submerged ; 
8    =  Specific  gravity; 

We  have — 

8_       _W  _ 

«      \V-\V, 


16 


BY  DENSIMETER. 


FORM  OF  EECORD  OF  COMPUTATION, 

Fort  Pitt  Foundry, 


Calibre. 

No. 

Spec. 

Temp 

Weight. 

Grains. 

Grains. 

Temp. 

Log. 

8p.  Gr. 

1910 

H.  1 

63° 

Tank  filled  

8962  1  ) 

63° 

1  9999020  ) 

Spec,  in  air  

9845  5  \ 

18807  6 

3  9932378  \ 

17465  0 

3  9931398 

Water  displaced  . 

1342  6 

3  1279466 

.  8651932 

7.332 

IX-inch  

1910 

H.  2 

63° 

8962.  1  > 

63° 

1  9999020  ^ 

9787.2J 

18749.  3 

3.  9906585  ) 

17416.  5 
1332.  8 

3.  9905605 
3  1247650 

.  8657955 

7.342 

1910 

H.  3 

63° 

8962.  1  ) 

63° 

1  9999020  \ 

9899.  6  J 

18861.7 

3.  9956176  ] 

17513.  5 
1348.2 

3.  9955196 
3.  1297543 

.8657653 

7.341 

IX-inch  shell  gun  .  . 

1912 

H.I 

63° 

8962.1  > 
9872.  5  5 

18834.6 

63° 

1.  9999020  ? 
3.9944271  $ 

17487.2 
1347  4 

3.  9943291 
3  1294965 

.  86483-26 

7.325 

IX-inch  

1912 

H.  2 

63° 

8962.1  ) 

63° 

1.9999020  ) 

9846.  6  5 

18808,7 

3.  9932863  $ 

17467.  3 
1341  4 

3.9931883 
3  1275583 

.  8656300 

7.339 

IX-inch  

1912 

H.  3 

63° 

8962.  1  ) 

63° 

1.  9999020  \ 

9724  0  ) 

18686  1 

3.  9878450  $ 

17361  3 

3.  9877470 

1324  8 

3.  1221503 

.  8655967 

7.338 

FORM  OF 

Report  of  the  density  and  tensile  strength  of  the  specimens  taken 


Calibre. 

Foundry 
mark. 

Specimen. 

Temp. 

tank. 

Density  hy 
densimeter. 

Temp, 
hydro. 

Density  by 
hydro. 

Diff.  of 
temp. 

No.  1910 

H.  1 

63° 

7.332 

64° 

7.330 

1° 

1910 

H    2 

63° 

7  342 

7.341 

1910 

H   3 

63° 

7  341 

7.340 

No.  1912 

H.  1 

63° 

7.325 

64° 

7.324 

1° 

1912 

H    2 

63° 

7  339 

7.338 

1912 

H    3 

63° 

7  338 

7.340 

17 


ORDNANCE-YARD,  WASHINGTON. 
Atacmfor  19,  1863. 


BY   HYDROMETER. 


Calibre. 

No. 

Spec. 

'emp. 

Weight. 

Grains. 

(ilains. 

Log. 

8p.  Or. 

1910 

H  1 

64° 

Bal.  of  hyd  

12784.  2  ) 

64° 

1.9998660  ) 

Bal.  with  spec,  in  air 

2938.5$ 

'.M.i.  . 

3.9932466$ 

Spec,  in  water  

4281.3 

1342.8 

3.9931126 
3.1280113 

.8651013 

7.330 

IX.inch    

1910 

H.  2 

64° 

12784.  2  ) 

64° 

2996.7  $ 

3.  9906718  $ 

4329.6 

1332  9 

3.  99U537H 
3  1247976 

• 

.8657402 

7.341 

IX-inch  

1910 

H.  3 

64° 

12784.2? 

64° 

1.9998660) 

2884.7  $ 

3.9956133$ 

Water  displaced 

4332.9 

1348  2 

3.  99M793 
3.  1297543 

.8657250 

7.340 

IX-inch  

1912 

H.  1 

64° 

12784.2) 

64° 

1.9998660  ) 

2911.8J 

9872.4 

3.  9944227  $ 

Water  displaced 

4259.4 

1347  6 

3.  99428*7 
3  1295610 

.8647277 

7.324 

IX-inch  

1912 

H.  2 

64° 

12784.  2  ? 

64° 

1.9998660  ) 

2937.8$ 

9846.4 

3.  9932775  $ 

45279.2 

'1341.4 

3.9931435 
3  1275583 

.8655852 

7.338 

IX-inch  

1912 

H.3 

64° 

12784.2  1 

64° 

1  9998660  ( 

3060.2  | 

9724.0 

3.9878450$ 

Water  displaced  .. 

4384.6 

1324  4 

3.9877110 
3  1220192 

.8656918 

7.340 

REPORT. 

from  the  following  cannon,  Fort  Pitt  Foundry,  Pitt-tburg,  Pa. 


Actual  density. 

Mean  density. 

Ilium,  of 
specimen. 

Breaking  weight. 

Tensile  strength. 

Mean  tent.  str. 

Date,  when  received,  Ac. 

7.331 

r.M 

7.341 
7.326 
7.330 
7.339 

7.338 
7.334 

1.20 
1.20 

Pound$. 
SfHMK) 
390(10 
%NXN) 
S7700 
37800 

asm 

1'nanils. 

am 

3448(1 

.:\\-> 

:m.\n 

::.:i-.'» 
33600 

34187 

MM 

Received  November  19,  1863. 
Broken  November  24,  1863. 

3 

18 


TENACITY. 

After  the  density  is  ascertained,  and  before  the  sample  is  inserted  in  the  pincers  for  the 
tensile  test,  its  smallest  diameter  in  the  middle  is  accurately  measured  by  the  specimen  calipers, 
and  recorded.  The  breaking  weight  is  divided  by  the  area  of  its  smallest  diameter,  and  the 
quotient  gives  the  tenacity,  or  the  strength  per  square  inch. 

In  order  to  obtain  reliable  comparative  results,  it  is  necessary  that  the  specimens  shall  all  conform  to  the 
standard  in  size  and  shape  ; 

The  breaking  strain  be  applied  slowly  and  gradually; 

That  the  specimen  he  placed  fairly  in  the  clamps,  so  that  it  is  not  subjected  to  a  strain  of  torsion  with 
that  of  extension. 


EXAMPLE. 


Sample  No.  4  H,  from  gun  head  : 


Breaking  weight,  50500 

Diameter,  1.25.     Area,  1.22719  , 


Logarithms. 
4.7032914 
0  0889099 


Tenacity,  or  strength  per  square  inch,  41151  pounds 4.6143815 

The  following  table  contains  the  areas  and  the  logarithms  for  all  the  variations  of  diameter 
likely  to  occur  in  tensile  samples: 


Diam. 

Area. 

Logarithms. 

Diam. 

Area. 

Logarithms. 

Diam. 

Area. 

Logarithms. 

1.190 

1.  11220 

.  0461839 

1.204 

1.  13853 

.  0563429 

1.297 

1.32120 

.  1209698 

1.191 

1.11407 

.0469135 

1.205 

1.  14042 

.  0570639 

1.298 

1.32324 

.  1216393 

3.192 

1.11594 

.  0476425 

1.206 

1.  14231 

.  0577845 

1.299 

1.  32528 

.  1223083 

1.193 

1.  11782 

.  0483707 

1.207 

1.  14421 

.  0585045 

1.300 

1.  32732 

.  1229767 

1.194 

.11969 

.  0490985 

1.208 

1.14610 

.  0592237 

1.301 

1.32937 

.  1236446 

1.195 

.  12157 

.  0498257 

1.209 

1.  14800 

.  0599425 

1.302 

1.33141 

.  1243120 

1.196 

.  12345 

.  0505523 

1.210 

1.  14990 

.0606607 

1.303 

1.33346 

.  1249788 

1.197 

.  12533 

.  0512783 

1.290 

1.  30698 

.  1162693 

1.304 

1.33550 

.  1256451 

1.198 

.  12721 

.  0520035 

1.291 

1.  30901 

.  1169423 

1.305 

1.33755 

.  1263109 

1.199 

.  12909 

.  0527283 

1.292 

1.31104 

.1176148 

1.306 

1.33960 

.  1269763 

1.200 

.  13097 

.  0534523 

1.293 

1.31307 

.  1182868 

1.307 

1.  34165 

.  1276411 

1.201 

.13286 

.  0541759 

1.294 

1.  31510 

.  1189583 

1.308 

1.  34370 

.  1283033 

1.202 

.13475 

.  0548989 

1.295 

1.31713 

.1196293 

1.309 

1.34576 

.  1289691 

1.203 

.13664 

.0556211 

1.296 

1.31917 

.  1202998 

1.310 

1.  34782 

.  1296325 

19 

INSPECTIONS    OF    NEW    GUNS. 

New  guns  are  to  be  closely  examined  and  measured,  inside  and  out,  for  defects  of  metal  or 
manufacture,  aud  the  results  recorded  in  the  prescribed  forms  by  the  Inspector  resident  at  the 
foundry,  as  soon  after  being  finished  as  possible,  if  he  has  not  already  done  so  in  the  various 
stages  of  manufacture,  which  is  preferable,  as  the  detection  of  errors  which  pass  the  limits  of 
toleration  may  save  useless  subsequent  labor.  Internal  defects  of  metal  will,  for  instance, 
generally  be  betrayed  by  a  close  examination  of  the  core  pieces.  As  rust  tends  to  conceal 
defects,  this  examination  of  the  guns  is  to  take  place  before  exposure  to  the  weather.  And 
previously  to  the  final  examination  and  proof  of  guns,  they  are  not  to  be  covered  with  paint, 
lacquer,  oil,  or  any  material  which  may  hide  defects  of  metal. 

If  it  is  ascertained  that  any  attempt  has  been  made  to  conceal  defects,  the  gun  or  guns  so 
treated  are  to  be  rejected  without  further  examination. 

As  the  water-proof,  which  is  of  great  importance  in  detecting  defects  of  metal  not  other- 
wise developed,  necessarily  succeeds  immediately  the  powder-proof,  and  can  be  effectively 
applied  only  in  fine  weather  and  when  the  temperature  is  above  the  freezing  point,  final  inspec- 
tions are  to  be  made  at  such  times  only. 

DESCRIPTIVE  LIST  OF  INSTRUMENTS  REQUIRED  AND  USED  IN  THE   INSPECTION  AND 

PROOF   OF  GUNS. 

1st.  A  mirror  for  reflecting  the  sun's  rays  into  the  bores.  Two  will  be  required  if  the  sun 
be  in  rear  of  the  inspector. 

2d.  A  lamp  attached  to  a  staff  for  examining  the  bores  when  the  sun  is  obscured,  or  the 
guns  are  under  cover. 

3d.  A  standard  cylinder  gauge.  This  is  a  hollow  cylinder  of  iron,  turned  to  the  least 
allowed  diameter  of  the  bore,  and  one  calibre  in  length.  It  has  a  cross-head  at  each  end,  one 
of  which  has  a  smooth  hole  through  its  axis  to  fit  the  staff,  and  the  other  is  tapped  to  receive 
the  screw  in  the  end  of  it. 

4th.  A  measuring  staff  of  steel  or  iron,  in  joints  of  suitable  length,  which  are  connected 
together  by  screws.  Each  joint  is  provided  with  a  light  brass  disc,  the  diameter  of  which  ia 
0.05  inch  less  than  that  of  the  bore.  Through  the  centre  of  the  disc  there  is  a  hole  which 
fits  upon  a  shoulder  at  the  joint;  the  whole  is  so  arranged  that  when  the  joints  are  screwed 
together  the  discs  between  them  are  held  firmly  in  place,  while  the  length  of  the  staff  is  not 
affected  by  them.  A  sled  point  is  screwed  on  to  the  end.  When  pushed  to  the  bottom  of  the 
bore,  the  staff  coincides  very  nearly  with  its  axis.  The  outer  joint  is  graduated  to  inches 
and  tenths.  A  slide  is  made  to  play  upon  it  with  a  vernier  scale,  graduated  to  hundredths 
of  an  inch.  On  the  inner  end  of  the  slide  a  branch  projects  at  a  right  angle,  sufficiently  long 
to  reach  across  the  muzzle  face,  and  when  in  contact  with  it  to  indicate  the  precise  length 
obtained  from  that  point  to  the  end  of  the  measuring  point  on  the  other  end  of  the  staff. 
A  half  disc  of  wood,  made  to  fit  the  bore,  with  a  groove  for  the  staff  to  rest  in,  placed  just 
inside  of  the  muzzle,  is  useful  in  preventing  any  springing  of  the  staff. 


20 

The  point  being  taken  off,  the  staff  can  be  used  with  the  cylinder  gauge  to  measure  the 
distance  to  which  the  latter  descends.  But  as  the  graduation  is  intended  for  the  points,  care 
must  be  taken  in  this  case  to  allow  for  the  difference. 

5th.  A  chamber  gauge  for  verifying  the  shape  and  size  of  conical  chambers. 

The  head  should  be  made  of  close-grained,  well-seasoned  wood,  and  of  the  exact  dimensions 
of  the  chamber.  Two  planes  crossing  each  other  at  a  right  angle,  coinciding  with  the  vertical 
and  horizontal  central  sections,  have  been  found  better  than  a  solid  block.  The  edges  should 
be  bevelled.  A  metal  socket  in  its  centre  connects  it  with  the  measuring  staff.  Being  pushed 
to  the  bottom  of  the  bore,  if  the  length  coincides  with  that  obtained  by  the  point,  it  is  obvious 
that  the  chamber  is  large  enough,  provided  the  cylindrical  part  has  not  been  bored  too  deep, 
in  which  case  a  shoulder  would  be  found  at  the  junction.  The  edges  of  the  gauge  should  be 
chalked  before  it  is  inserted.  When  withdrawn,  if  the  chalk  marks  are  visible  all  around  the 
chamber,  it  is  evident  that  the  chamber  is  not  too  large.  With  slight  modifications,  this 
arrangement  may  be  applied  to  the  slope  of  cylindrical  chambers,  and  to  the  curve  at  the 
bottom  of  the  bore  of  any  guns.  Should  the  inspection  of  guns  with  conical  chambers  or 
slopes  take  place  at  the  foundry,  an  examination  of  the  chamber  reamer  will  be  very  satis- 
factory. If  found  correct  in  size  and  shape,  the  impossibility  of  making  the  chamber  too  large 
will  be  apparent. 

6th.  A  star  gauge,  for  measuring  the  udiameters  of  the  bores  and  of  cylindrical  chambers. 
This  instrument  is  composed  of  the  staff",  the  handle  and  a  set  of  points  for  each  calibre. 

The  staff  is  a  brass  tube,  made  in  three  pieces,  for  convenience  of  stowage,  and  connected 
together,  when  required,  by  screws.  Its  inner  end  expands  into  a  head,  in  which  are  placed 
four  steel  sockets,  at  equal  distances  from  each  other,  which  receive  the  points.  Two  of  the 
sockets  opposite  to  each  other  are  secured  permanently.  The  two  others  are  movable.  A 
tapering  plate  or  wedge,  the  sides  of  which  are  cylindrical,  runs  through  a  slit  in  the  head; 
an  aperture  in  the  inner  ends  of  the  movable  socket  embraces  the  cylinder,  so  that  when  the 
plate  is  moved  forward  or  backward,  the  sockets  are  projected  or  withdrawn.  The  tapering 
of  the  plate  has  a  certain  known  proportion  to  its  length,  so  that  if  it  is  moved  in  either 
direction  a  given  distance,  a  proportional  movement  is  imparted  to  the  sockets,  and  to  the 
points  which  they  contain.  It  is  easy  to  see  how,  in  this  manner,'  a  movement  of  .10  in. 
may  increase  or  diminish  the  distance  between  the  points  .01  in.  Therefore  there  would 
be  no  difficulty  in  estimating,  to  a  considerable  degree  of  accuracy,  a  difference  of  .001  in. 
between  the  points.  In  general,  however,  the  distance  on  the  plate  required  to  move  the 
points  .01  in.  is  about  .06  in.  only. 

A  square  sliding-rod  is  connected  with  the  tapering-plate,  and  runs  through  the  whole 
length  of  the  tube,  projecting  some  inches  beyond  the  outer  end.  This  rod  has  as  many  parts 
as  there  are  joints  in  the  staff,  and,  like  them,  connects  by  screws.  Bach  section  of  the  rod 
works  in  its  proper  joint,  through  a  square  socket  at  each  end,  and  is  prevented  from  falling 
out  by  pins.  When  screwing  the  joints  together,  if  the  ends  of  the  rod  are  pressed  up  to  each 
other  they  become  connected  by  the  same  motion. 


21 

The  staff  is  graduated  to  inches  and  quarters,  so  that  the  distance  of  the  points  from  the 
ninz/.le  of  the  gun  may  always  be  known.  A  centre  line,  starting  from  the  centre  of  the  upper 
socket,  id  marked  upon  the  staff  throughout  its  length. 

The  handle  in  use  at  present  is  of  brass,  made  to  fit  over  the  outer  end  of  the  staff,  and 
to  connect  with  the  sliding-rod  by  a  screw,  having  a  large  milled  head  at  the  outer  extremity 
of  the  handle.  It  may  bo  used  on  either  joint,  as  required.  A  slit  through  the  handle  permits 
a  part  of  the  staff  near  the  end  to  be  seen  beneath.  A  scale  on  one  side  of  the  slit  is  graduated 
with  the  distance  that  the  rod  moves,  to  throw  the  points  .01  in.  apart. 

That  part  of  the  handle  containing  the  slit  and  scale  is  separated  from  the  other  part;  it 
is  made  to  fit  closely  over  it.  On  each  side  there  is  a  small  tube;  a  thread  is  cut  in  one,  through 
which  a  fine  screw,  held  by  a  stud  on  the  permanent  part  of  the  handle,  works  and  gives  it 
motion;  a  guide  runs  through  the  other.  Seen  through  the  slit  is  a  small  plate  of  silver 
inserted  in  the  staff,  and  a  fine  mark  upon  it  to  show  the  place  of  zero,  when  the  points  are 
adjusted.  The  zero  mark  on  the  scale  is  made  to  correspond  with  it  by  means  of  the  screw 
just  mentioned. 

The  points  are  of  steel,  with  a  strong  shoulder  at  one  end,  below  which  the  screw  is  cut 
that  fits  into  the  socket  in  the  head.  A  wrench  is  made  to  fit  the  other  end  so  as  to  turn  the 
point  firmly  into  its  place.  They  are  made  of  such  a  length  that  they  will  just  pass  into  the 
adjusting  ring  when  they  are  all  in  place.  To  this  instrument  belong  the  adjusting 
rings  and  the  muzzle  rest  in  the  form  of  T  ;  of  the  rings  there  is  one  for  each  calibre,  reamed 
out  to  the  exact  minimum  diameter  of  the  bore.  The  latter  can  be  used  for  any  class  of 
gnns.  Its  office  is  to  keep  the  staff  of  the  star  gauge  in  the  axis  of  the  bore.  For  this 
purpose  it  contains  a  groove,  above  the  perpendicular  branch,  to  receive  the  lower  half  of 
the  staff.  There  is  a  movable  slide  on  each  branch,  which  can  be  adjusted  to  marks  for 
each  calibre,  so  that  points  projecting  from  their  rear  will  enter  the  muzzle  and  hold  the 
rest  in  place.  In  this  position  the  upper  edge  of  the  transverse  branch  coincides  with  the 
diameter  of  the  bore. 

A  hook  is  pivoted  on  the  innef  side  of  the  transverse  branch,  on  one  side  of  the  groove, 
and  so  fitted  that  when  the  star  gauge  is  in  the  gun,  it  embraces  one-half  of  that  portion 
of  the  staff  which  is  above  the  groove.  Therefore,  if  the  transverse  branch  be  placed  so 
as  to  coincide  with  the  axis  of  the  trunnions,  the  hook  thrown  over  the  staff,  and  the  latter 
turned  so  that  the  centre  line  just  meets  the  end  of  the  hook,  the  perpendicular  points  will 
be  perpendicular  to  the  axis  of  the  trunnions.  If  the  staff  is  then  drawn  out  carefully,  the 
measurements  will  all  be  taken  in  the  same  plane.  A  notch  in  the  end  of  the  hook,  made  to 
coincide  with  the  plane  of  the  muzzle,  may  be  used  for  marking  the  distances  on  the  staff. 

The  upright  branch  is  movable,  and  is  made  to  fit  into  the  end  of  the  transverse  branch 
for  convenience  and  security  in  packing. 

In  examining  the  bores  after  proof,  it  has  been  found  that  the  greatest  indentation  occurs 
in  general  near  the  seat  of  the  projectiles.  But  as  it  is  not  always  found  at  precisely  the  same 
point  of  the  circle  of  the  bore,  a  convenient  mode  of  searching  for  it  is  desirable.  This  ia 


22 

supplied  by  a  disc  for  circular  measurements,  which  may  also  be  considered  as  belonging  to  the 
star  gauge.  It  is  made  of  composition,  and  is  divided  into  halves,  with  a  hole  through  the 
centre  to  receive  the  staff  of  the  star  gauge. 

It  is  turned  so  as  to  fit  into  the  muzzle  of  the  gun  closely,  with  a  projecting  lip  two  or 
three  inches  broad  to  hold  it  in  place,  and  with  cleats  overlapping  the  edges,  to  keep  it  from 
going  in  too  far.  The  face  is  a  plane  surface.  The  circumference  is  divided  into  as  many 
equal  parts  as  may  be  thought  desirable,  which  are  numbered  in  regular  order.  The  centre 
hole  is  reinforced  on  the  inside  by  a  projection  which  is  turned  to  receive  a  collar  that  fits 
closely  around  it,  and  holds  the  two  halves  together  when  they  are  placed  on  the  staff. 

When  ready  for  use,  the  face  is  in  the  plane  of  the  muzzle  face.  Its  zero  mark  is  made 
to  coincide  with  a  light  punch  mark  on  the  muzzle  face,  directly  below  the  line  of  sight. 

On  the  staff  of  the  star  gauge  a  brass  slide  is  fitted,  having  a  thumb-screw  to  hold  it  in  any 
position;  from  the  inner  end  a  point  extends  at  a  right  angle  to  its  axis,  of  sufficient  length  to 
meet  the  points  at  the  circumference  of  the  disc;  a  centre  line  extends  from  the  base  to  the 
apex.  The  slide  being  moved  so  as  to  make  its  inner  end  coincide  with  any  mark  upon  the 
staff,  at  which  a  circular  measurement  is  required,  and  the  centre  line  of  the  point  being  made 
to  coincide  with  that  of  the  staff,  it  is  secured  by  the  thumb-screw.  The  point  of  the  slide  is 
then  in  the  same  plane  with  the  perpendicular  measuring  points,  and  its  direction  always  indi- 
cates theirs;  a  series  of  measurements  made  before  proof  may  thus  be  compared  with  another 
made  at  the  same  points  after  proof. 

It  is  obvious  that  the  determinations  will  not  be  absolutely  accurate,  for  when  the  gun  is 
worn,  should  the  stationary  points  be  perpendicular,  the  movable  points  being  then  horizontal, 
would  fall  below  the  true  horizontal  diameter,  and  the  measurements  would  be  more  in  error 
than  it  would  be  with  the  points  in  any  other  direction.  Still,  if  care  is  taken  to  preserve  the 
points  at  the  greatest  length  possible,  a  very  tolerable  degree  of  accuracy  may  be  attained. 
In  the  inspection  of  guns  arranged  on  skids,  the  gun  itself  should  be  turned,  which  will  ensure 
accurate  measurements.  Care  must  also  be  taken  not  to  allow  the  joints  of  the  staff  to  be- 
come so  loose  that  the  coincidence  of  the  centre  line  is  destroyed  when  they  are  screwed 
together.  If  this  should  occur,  however,  a  few  turns  of  thread  placed  between  them  at  the 
time  of  putting  the  instrument  together  would  remedy  the  difficulty. 

7th.  An  instrument  for  verifying  the  interior  position  of  vents. 

When  the  vent  is  drilled  in  the  vertical  plane  of  the  axis,  as  in  the  guns  of  old  patterns, 
a  simple  head,  shaped  to  fit  the  bottom  of  the  bore,  or  the  chamber,  with  a  staff  fitted  to  it,  is 
sufficient.  But  for  the  Dahlgren  guns,  with  two  vents,  some  other  plsfti  is  better.  The  follow- 
ing has  been  found  satisfactory: 

A  head  of  well  seasoned  wood,  which  is  fitted  to  the  chamber,  is  attached  to  a  wooden 
disc  of  the  diameter  of  the  main  bore.  The  surface  of  the  head  corresponds  with  a  longitudinal, 
central  section  of  the  chamber;  at  the  point  where  the  projection  of  the  vent  would  meet  it  a 
piece  of  hard  wood  is  inserted.  A  central  line  drawn  through  its  length,  crossed  at  a  right 
angle  by  another  line  at  any  known  point  from  the  smaller  end,  will  afford  convenient  points 
to  measure  from.  A  stout  square  wooden  staff  is  attached  to  the  axis  of  the  head;  at  a  dis- 


23 

tanco  equal  to  the  length  of  the  bore,  the  end  is  jogged  into  the  centre  of  a  half  disc  of  wood, 
which  is  fitted  to.  the  bore.  The  whole  is  so  constructed  that  the  straight  edge  of  the  half 
disc  (or  the  chord)  is  in  the  same  plane  as  a  horizontal  section  of  the  head.  A  few  holes  are 
bored  through  the  disc  attached  to  the  half  head,  to  allow  the  instrument  to  pass  freely  into 
the  pm  and  out  of  it.  ^ 

A  wire  of  untempered  steel  of  the  size  of  the  vent,  with  a  sharp  well  centred  point,  and 
a  small  spirit  level,  are  required  to  use  with  this  instrument. 

The  gun  being  levelled,  and  the  instrument  being  pushed  to  the  bottom  of  the  bore,  the 
upper  edge  of  the  half  disc  near  the  outer  end  of  the  staff  is  then  brought  to  a  level.  The 
surface  of  the  half  head  then  corresponds  with  the  horizontal  central  section  of  the  chamber. 
The  point  of  the  wire  being  pushed  gently  to  meet  it,  will  show  very  accurately  the  interior 
position  of  the  vent. 

8th.  Profile  boards  for  distances  in  front  and  rear  of  the  base  line. 

Their  lower  edges  are  adapted  to  the  shape  of  the  gun,  and  the  upper  ones  are  parallel 
to  the  axis  of  the  bore. 

• 

The  distances  from  the  base  line  of  the  several  parts,  and  of  the  points  at  which  diameters 
are  to  be  measured,  are  laid  off  accurately  on  the  upper  edge,  and  then  marked  in  lines  perpen- 
dicular to  it  on  the  sides,  and  lower  edges  of  the  profile.  A  narrow  strip  is  attached  to  the 
upper  edge  to  prevent  warping,  and  the  whole  is  well  coated  with  shellac  varnish  to  keep  it 
from  absorbing  moisture. 

The  following  instruments  are  used  in  connexion  with  the  profile  boards  : 

A  rule  for  verifying  the  marks,  of  such  a  length  that  not  more  than  one  fleeting  may  bo 
necessary,  to  be  graduated  decimally  according  to  the  standard. 

A  small  square  of  steel,  to  be  used  in  referring  the  marks  on  the  board  to  those  on  the 
rule. 

A  steel  straight-edge,  long  enough  to  extend  across  the  muzzle-face,  and  several  inches  on 
the  board,  to  ascertain  the  extreme  length  from  base  to  muzzle.  It  is  also  used  for  the  same 
purpose  at  the  extreme  end  of  the  cascable.  A  steel  scratcher,  to  mark  the  gun  at  points  not 
otherwise  indicated,  where  diameters  are  to  be  measured. 

9th.  A  trunnion  square  of  steel  or  iron,  for  ascertaining  the  position  of  the  trunnions,  with 
reference  to  the  axis  of  the  bore.  This  instrument  is  a  square  with  two  branches,  one  of 
which  is  fixed  and  the  other  movable.  The  foot  of  each  branch  is  in  the  same  plane,  and  is 
parallel  to  the  upper  edge  of  the  main  piece  which  connects  them.  The  latter  is  graduated  to 
inches  and  tenths.  The  movable  branch  slides  on  the  main  piece,  and  may  be  secured  to  it  by 
two  thumb-screws.  It  is  provided  with  a  vernier  scale  graduated  to  hundredths  of  an  inch. 
Between  the  branches  there  is  a,  slide,n\so  provided  with  a  vernier  graduated  as  before,  with  a 
thumb-screw  to  secure  it  firmly;  in  its  centre  there  is  a  sliding  point,  moving  vertically,  with  a 
thumb-screw  to  fasten  it.  Above  the  foot  of  each  branch  there  is  a  slit  to  receive  the  shank  of 
a  plate,  on  the  end  of  which  a  thread  is  cut;  the  lower  edge  of  the  plate  forms  a  right  angle 
with  the  branch,  and  the  plate  is  fastened  to  the  branch  by  a  nut,  at  a  point  from  tlio  end 
equal  to  the  semi-diameter  of  the  trunnion,  which  is  marked  on  each  branch. 


24 

When  the  feet  of  the  branches,  or  the  lower  edge  of  the  plates,  rest  upon  the  trunnions, 
the  upper  edge  of  the  main  piece  is  parallel  to  their  axis,  if  their  alignment  is  correct.  "When 
in  the  latter  position,  the  edges  of  the  feet  will  lie  close  against  the  sides  of  the  trunnions. 

A  graduated  steel  wedge  is  used  to  measure  the  deviation  of  the  trunnions  from  the  feet  of 
the  square. 

10th.  A  trunnion  gauge,  which  is  an  iron  ring  of  the  proper  diameter  of  the  trurfnions. 
Its  outer  edge  coincides  with  the  diameter  of  the  rimbases. 

llth.  A  trunnion  rule  to  measure  the  distance  of  the  trunnions  from  the  base  ring,  or  line. 
This  is  an  iron  rod  with  a  head  at  one  end,  through  which  passes  one  branch  of  a  small  square. 
The  centre  of  the  rod  is  marked  on  the  end,  and  the  square  is  set  so  that  the  inner  edge  of 
the  branch  which  is  parallel  to  the  rod  is  at  a  distance  equal  to  the  semi-diameter  of  the  trun- 
nion from  the  centre.  It  is  secured  in  this  position  by  screws  and  clamps. 

The  upper  side  of  the  rod  is  graduated  to  inches  and  tenths.  A  slide  with  a  slot  through 
it,  to  show  the  graduation  beneath,  traverses  upon  it,  and  is  kept  from  turning  by  a  guide  on 
the  lower  side.  There  is  a  vernier  upon  the  slide  graduated  to  hundredths  of  an  inch;  a 
thumb-screw  serves  to  secure  the  slide  at  any  point  on  the  rod.  That  end  of  the  slide  from 
which  the  graduation  of  the  rod  commences  has  both  of  its  sides  drawn  out  to  form  knife 
edges;  the  knife  edges  and  the  end  of  the  slide  are  in  the  same  plane.  When  the  square  at  the 
end  is  placed  on  the  trunnion,  the  end  of  the  rod  will  touch  its  side  at  the  point  of  its  greatest 
diameter.  The  rod  being  held  parallel  to  the  axis  of  the  bore,  with  the  side  of  the  head 
pressing  the  rimbase,  the  knife  edge  will  be  in  a  proper  position  to  fall  into  the  base  line  when 
moved  to  find  it. 

12th.  A  beam  calliper  for  measuring  diameters  is  a  square  of  steel  or  iron,  with  two 
branches,  one  of  which  is  fixed  and  the  other  sliding.  The  inner  edges  of  the  two  branches, 
when  pushed  together,  lie,  of  course,  in  contact  with  each  other  throughout  their  length. 
The  beam  is  graduated  to  inches  and  tenths.  A  vernier  is  attached  to  the  sliding  branch, 
graduated  to  hundredths  of  an  inch.  The  latter  is  provided  with  a  thumb-screw  to  fasten  it  at 
any  point. 

The  length  of  the  beam  must  be  rather  greater  than  the  diameter;  and  that  of  the 
branches  than  the  semi-diameter  of  the  guns  to  be  inspected,  at  their  largest  points. 

13th.  A  cascable  block  is  a  wooden  cylinder  of  the  proper  diameter  of  the  breeching  hole, 
the  size  of  which  is  used  to  verify. 

The  opening  between  the  jaws  may  be  ascertained  by  measuring  the  iron  block,  which  ia 
fitted  to  go  between  them,  or  by  a  template. 

14th.  A  vent  guide,  to  be  used  with  vents  in  guns  of  Dahlgren's  pattern. 

This  instrument  is  made  of  bronze  or  composition.  When  placed  upon  the  gun,  one 
of  its  branches  coincides  with  the  curve  of  the  cylinder,  and  the  other,  starting  from  its  centre, 
lies  along  the  cylinder  in  contact  with  it  longitudinally.  The  lower  edges  of  the  branches  are 
a  right" line  and  a  curved  line,  making  two  right  angles  with  each  other.  The  length  of  that 
of  the  transverse  branch  is  equal  to  the  distance  between  the  centre  of  the  two  vents.  The 
rear  surface  of  the  transverse  branch  is  curved  and  quadrilateral.  Its  sides  are  inclined,  so 


25 

that  their  rear  edges  show  the  exact  direction  of  the  vents.  Every  point  in  the  upper  edge 
jies  in  the  same  horizontal  plane.  The  height  is  sufficient  to  permit  the  edges  to  give  an 
accurate  direction  to  the  drill. 

The  upper  edge  of  the  other  branch  runs  off  in  a  sloping  curve  to  its  extremity. 

A  centre  line  is  drawn  through  the  lower  edge  of  the  longitudinal  branch,  and  is  continued 
upwards  on  the  rear  surface  of  the  transverse  branch  to  the  top. 

The  guide  being  placed  with  its  centre  upon  the  centre  mark  of  the  gun,  and  the  centre 
line  of  the  longitudinal  branch  being  made  to  coincide  with  the  centre  line  scribed  upon  the 
cylinder,  the  rear  lower  edge  of  the  transverse  branch  will  then  coincide  with  the  base  line,  ita 
extremities  will  indicate  the  centres  of  the  vents,  and  the  rear  edges  of  the  sides  will  show 
their  true  direction. 

15th.  Vent  gauges  of  untempered  steel  wire,  with  shoulders  to  prevent  them  from  slipping 
into  the  vent.  One  should  be  of  the  proper'diameter  of  the  vent,  one  of  the  greatest,  and  one 
of  the  least  diameter  allowed. 

16th.  A  vent  searcher,  a  steel  wire  of  the  length  of  the  vent,  bent  to  a  right  angle  at  the 
lower  end  and  pointed.  It  is  used  for  detecting  imperfections  in  the  sides  of  the  vents. 

17th.  A  semicircular  protractor  of  metal  for  measuring  the  inclination  of  vents,  or  for 
ascertaining  their  deviation  from  the  guide. 

18th.  A  set  of  templates  for  verifying  the  shape  of  lock-lugs,  the  angle  of  the  rear  sight 
mass,  the  curve  between  the  base  line  and  the  front  of  rear  sight  mass,  that  at  the  end  of  the 
cascable,  the  bevel  of  the  breeching  hole,  the  opening  of  the  cascable,  the  shape  of  the  muzzle 
swell,  <tc. 

If  the  inspection  should  take  place  at  the  foundry,  the  templates  used  in  chipping  might 
be  verified  and  used  for  inspection. 

For  guns  of  Dahlgren'a  pattern,  a  bronze  model,  showing  the  shape  of  the  lugs  and 
rear  sight  mass,  and  the  position  of  the  vents,  has  been  furnished  as  a  guide  to  the  contractors. 

19th.  A  standard  foot-rule  for  verifying  measures. 

20th.  A  foot-rule  of  steel  for  measuring  the  masses,  the  length  of  the  trunnions,  and  for 
other  purposes.  The  graduation  should  be  extended  to  each  end. 

21st.  A  set  of  ring  gauges,  large,  medium,  and  small,  for  inspecting  the  projectiles  used  in 
proof. 

22d.  A  small  beam  calliper,  with  outside  edges,  for  examining  the  adjusting  rings  and  the 
ring  gauges. 

23d.  A  platform  balance  for  weighing  the  projectiles  used  in  proof,  and  for  bringing  the 
shells  up  to  the  standard  weight.  For  use  with  the  above  there  should  be  provided  a  bag  of 
dry  sand,  a  funnel,  some  toooden  plugs  for  the  fuze  holes,  and  a  hammer. 

24th.    A  set  of  implements  for  loading  and  cleaning,  viz  :  , 

A  rammer,  faced  with  hard  wood  or  metal,  with  a  graduated  scale  on  the  staff,  near  the 
muzzle,  to  show  the  distance  of  the  front  of  the  projectiles  from  the  muzzle. 

A  bristle  sponge  with  a  worm  in  its  end,  for  ordinary  use  in  firing. 


26 

A  sheepskin  sponge,  for  drying  the  bore  after  cleaning  it. 

A  gun  scraper. 

A  ladle. 

A  boring  bit. 

A  priming  wire. 

A  lock  and  laniard,  should  navy  primers  be  used  in  firing;  but  if  friction  primers  are  used, 
then  a  laniard  with  a  hook  in  its  end  will  be  required,  only. 

A  breeching  and  a  couple  of  tackles,  if  the  guns  should  be  fired  on  skids. 

pix  handspikes. 

Six  buckets  and  a  large  tub,  for  washing  out  the  guns. 

And  if  the  firing  is  made  into  a  butt,  then  a  couple  of  wheelbarrows,  with  two  or  three 
pickaxes,  and  half  a  dozen  shovels,  will  be  necessary. 

25th.  A  searcher,  with  six  or  more  points,  to  detect  injuries  or  cavities  in  the  bore. 

26th.    A  machine  for  taking  the  interior  impression  of  vents. 

This  consists  of  a  wooden  head,  one-half  of  which  is  cylindrical,  and  the  other  half  is  of 
the  shape  of  the  chamber,  both  being  rather  smaller  than  the  .parts  of  the  bore  that  they  are 
intended  for.  A  staff,  flat  on  its  upper  side,  and  rounded  on  its  under  side  to  fit  the  curve  of 
the  bore,  is  mortised  into  the  circumference  of  the  cylindrical  part  of  the  head.  A  mortise  is  cut 
through  the  chamber  part  of  the  head,  extending  several  inches  in  rear  and  front  of  the  position  of 
the  vent.  Into  this  mortise  a  loose  piece  is  fitted,  capable  of  free  motion  upwards  and  downwards, 
the  top  of  which  is  fitted  with  holes  to  secure  the  wax  or  composition  which  is  spread  over  its 
surface.  This  movable  piece  rests  on  a  wedge  attached  to  a  flat  rod  running  through  a  slot  in 
the  head;  there  is  a  slot  in  this  rod  about  four  inches  long,  a  pin  passing  through  it  into  the  staff. 
To  use  the  instrument,  withdraw  the  rod  as  far  as  the  slot  will  permit,  which  will  allow  the 
movable  piece  on  which  the  composition  has  been  spread,  to  drop  below  the  surface  of  the  head, 
and  protect  it.  Push  the  head  to  the  bottom  of  the  chamber,  and  arrange  the  position  of  the 
staff  so  that  the  movable  piece  will  cover  the  vent,  then  press  the  end  of  the  rod  home.  This 
motion  will  throw  out  the  composition,  and  a  distinct  impression  of  the  vent  and  of  fire  cracks, 
(should  there  be  any,)  will  be  left  upon  its  surface;  draw  the  rod  back  as  far  as  tbe  slot  will 
allow,  and  withdraw  the  instrument:  the  impression,  being  protected  thereby,  will  come  out 
uninjured. 

Impressions  of  injuries  or  cavities  in  the  bore  may  easily  be  taken  by  a  similar  contrivance. 

27th.  Hydraulic  pump  and  apparatus  for  the  water-proof. 

Any  of  the  various  patterns  of  this  machine  may  be  applied  to  the  proof  of  guns.'  An  iron 
cross-head  is  secured  to  a  stout  wooden  block  which  fits  into  the  muzzle,  and  which  has  a  flange 
or  shoulder  to  cover  the  muzzle-face  ;  rings  of  caoutchouc  or  gutta-percha  are  placed  between 
them;  an  iron  rod  with  a  ring  in  oue  end,  to  fit  over  the  trunnion,  and  with  a  thread  cut  on 
the  other  end,  is  used  on  each  side  of  the  gun,  to  cqnnect  the  trunnion  with  the  cross-head. 
The  whole  is  set  up  with  nuts,  and  the  pressure  upon  the  rings  makes  a  tight  joint;  a  coupling 
upon  the  cross-head  receives  the  hose,  and  the  water  is  forced  into  the  gun  through  a  hole  in 

the  wooden  block.      Care  should  be  taken  that  the  valve  is  loaded  with  the  proper  weight  for 

* 

proof. 

28th.  Dies  for  marking  guns.     A  full  set  of  figures,  with  such  capital  letters  as  may  be 
required  for  the  inspection  marks;  these  should  be  one  inch  in  length.     Also,  small  letters  o 
suitable  size  to  mark  "Ibs.,"  and  a  full  set  of  half-inch  figures. 


27 

USE  OF  THE  INSPECTING  INSTRUMENTS. 

The  guns  having  been  freed  from  rust,  and  their  foundry  numbers  noted,  in  the  order  of 
their  relative  positions,  ou  the  field-book,  the  inspecting  officer  will  proceed  to  verify  the  in- 
struments to  be  used  in  their  measurement,  if  this  has  not  been  previously  done  in  a  manner 
entirely  satisfactory  to  him. 

He  will  then  examine  carefully  the  guns,  inside  and  out,  for  defects  of  metal  or  of  manu- 
facture, and  note  the  results. 

The  interior  of  the  bore  is  to  be  examined  by  reflecting  the  rays  of  the  sun  into  it  from  a 
mirror  or  mirrors;  or,  if  the  sun  is  obscured  awl  there  can  be  no  delay,  by  means  of  a  spirit-lamp, 
or  of  a  wax  taper,  on  the  end  of  a  rod,  taking  care  not  to  smoke  the  surface  of  the  bore. 

The  cylinder  gauge  is  then  to  be  introduced,  which  must  pass  freely  to  the  bottom  of  the 
cylindrical  part  of  the  bore.  If  obstructed,  the  depth  to  which  it  reaches  should  be  noted. 

The  star  gauge  is  used  to  ascertain  the  exact  diameter  of  the  bore,  and  of  the  cylindrical 
part  of  the  chamber.  The  bore  must  be  measured  at  intervals  of  \  inch  from  the  bottom  of 
the  cylindrical  part  to  the  seat  of  the  shot;  of  1  inch  from  that  point  to  the  trunnions;  and  of 
5  inches  from  the  trunnions  to  the  muzzle.  If  any  marks  of  the  reamer  or  other  defects  are 
seen  in  the  bore,  they  are  to  be  searched  for,  and  their  depths  and  positions  noted.  These 
results  are  to  be  tabulated  according  to  the  blank  forms  furnished.  The  whole  length  of  the  bore 
is  ascertained  by  means  of  the  measuring  staff,  with  the  point  screwed  on,  supported  in  the 
axis  of  the  bore  by  the  discs  and  half-lampion. 

In  the  absence  of  this  instrument,  a  pine  rod,  having  the  proper  length  of  the  bore  marked 
on  it,  and  the  end  rounded  fo  the  curve  of  the  bottom  of  the  bore,  will  answer  as  well,  using 
a  thread  or  a  straight-edge  across  the  face  of  the  muzzle. 

The  shape  and  dimensions  of  the  chamber,  and  the  position  of  the  interior  orifice  of  the  vent. 
are  verified  by  means  of  the  chamber  gauge,  the  description  of  which  will  explain  its  use.  Ar 
inspection  of  the  chamber  reamer  will  be  generally  satisfactory  in  determining  the  size  and 
shape  of  the  chamber. 

The  vent  is  measured  by  the  appropriate  gauges,  the  smaller  of  which  must  enter  freely, 
anil  the  larger  not  at  all.  It  is  searched  for  roughness  or  for  cavities  in  the  metal  around  it, 
by  means  of  the  searcher,  the  point  of  which  should  feel  every  part  of  it  carefully. 

Its  inclination  to  the  surface,  and  its  position  externally,  is  verified  by  means  of  the  vent- 
guide  furnished  for  the  Dahlgren  guns,  and  by  the  semicircular  protractor  and  the  vent-gauge. 

In  guns  of  the  ordinary  construction  the  position  of  the  vent  is  marked  on  the  profile 
board,  and  its  inclination  to  the  surface  is  determined  by  the  protractor  and  vent-gauge. 

The  exterior  lengths  of  the  gun  are  measured  by  the  profile  board,  marked  with/  the  trne 
dimensions,  the  differences  being  measured  by  the  foot-rule,  or,  if  minute,  estimated  by  the  eye. 

The  exterior  diameters  are  measured  with  the  callipers  and  square,  or  by  the  set-gauges  used 
in  turning,  and  a  graduated  wedge. 

To  verify  the  position  and  alignment  of  the  trunnions  of  a  gun,  it  is  first  necessary  to  aecer- 


28 

tain,  by  means  of  the  trunnion  gauge  and  of  the  callipers,  their  cylindrical  form  and  their 
diameters,  which  should  bo  the  same,  or  allowance  must  be  made  for  half  the  difference  in 
measuring  their  axial  distances  from  the  base  line,  by  the  trunnion  rule,  which  should  next 
be  done.  These  distances  should  be  equal,  or  their  axes  do  not  coincide — an  error  not 
tolerated. 

The  trunnion  square  is  then  placed  upon  the  trunnions  in  the  plane  of  their  axis.  The 
feet  of  its  branches  should  coincide  with  the  surfaces  of  both  trunnions,  throughout  their  length, 
above  and  in  rear,  and  their  inner  edges  with  the  faces  of  the  rimbases.  Then,  with  the  beam 
compass,  scribe  on  the  upper  surface  of  the  gun  the  distance  of  the  axis  of  the  trunnions  from 
the  base  line,  and  push  the  sliding  point  of  the  square  down,  till,  at  that  distance,  it  touches 
the  surface  of  the  gun,  and  screw  it  fast.  Then  turn  the  gun  over,  and  again  scribe  on  it  the 
same  distance  from  the  base  line.  The  square  being  again  applied,  will  determine  whether 
the  trunnions  are  above  or  below  the  axis  of  the  bore,  which  will  coincide  with  that  of  the  gun, 
if  accurately  bored  and  turned  on  the  same  centres  and  bearings.  If  the  branches  rest  upon 
the  trunnions  before  the  point  of  the  slider  touches  the  gun  at  the  scribe,  their  axis  is  below; 
but  if  the  point  touch  first,  above  the  axis  of  the  bore,  by  half  the  space  between.  The 
graduated  wedge  being  placed  under  the  vertical  sliding  point  will  determine  the  amount.  If 
both  touch  at  once,  both  axes  are  in  the  same  plane. 

No  gun  can  be  received,  the  axis  of  the  trunnions  of  which  is  above  that  of  the  bore. 

The  lengths  of  the  trunnions  are  measured  with  the  foot-rule,  and  the  diameters  of  the 
rimbases  by  that  of  the  exterior  rim  of  the  trunnion  gauge. 

If  the  alignment  of  the  trunnions  be  correct,  it  will  serve  as  a  means  of  determining  the 
correctness  of  the  line  of  sight,  which,  before  the  gun  is  removed  from  the  lathe,  should  be 
distinctly  traced  on  the  sight-masses  and  the  swell  of  the  muzzle,  and  should  be  at  right 
angles  to  the  base  line,  to  the  axes  of  the  trunnions,  and  to  the  connecting  piece  of  the 
trunnion  square,  when  its  branches  rest  against  their  rear,  with  the  plates  across  their  upper 
surfaces. 

The  Inspector  will  further  satisfy  himself  of  the  correct  tracing  of  the  line  of  sight  on  the 
gun  by  examining  the  lathe  and  the  manner  of  tracing  it  in  the  plane  of  the  axis  of  the  bore, 
at  right  angles  to  the  axis  of  the  trunnions,  as  by  it  are  placed  the  sights  and  vent,  and  in  their 
absence  it  serves  as  a  line  of  metal  sight. 

The  positions  of  the  sight-masses  are  verified  by  the  profile  board,  and  by  reference  to  the 
line  of  sight,  traced  on  them;  their  form  and  dimensions  by  the  templates. 

The  positions  of  the  lock-lugs  and  their  forms  are  verified  by  means  of  the  bronze  pattern 
furnished  to  each  foundry  for  each  class  of  the  Dahlgren  guns,  and  their  dimensions  by  the 
templates.  For  other  guns  the  position  of  the  lock-piece  is  marked  on  the  profile  board,  and 
their  measures  taken  as  above. 

The  opening  of  the  cascable  and  its  curves,  and  those  of  the  breech  and  the  muzzle-swell, 
are  verified  by  means  of  the  "cylinder  Uoc/e"  and  the  templates. 


The  following  variations  from  the  proper  dimensions  may  be  tolerated  by  the  Inspector, 
though  every  effort  should  be  made  to  conform  exactly  to  the  drafts  furnished  by  the 
Bureau  of  Ordnance. 

Inch. 

T    ,.      ,.       A       ,  it     ,  f  more 0.03 

In  the  diameter  of  the  bore . .  J 

(  less 0.00 

f  where  1  more 05 

turned  or  planed  f  less ; OS 

Lxtenor  diameter <     , 

1  where  not  )  more 20 

(_  turned  or  planed  )  less 05 

!of  the  bore,  more  or  less 10 
from  rear  of  base  ring  or  line  to  face  of  the  muzzle,  more  or  less .25 
of  the  cascable,  from  rear  of  base  ring  to  the  end,  more  or  less SJO 
of  the  reinforce,  more  or  less 15 

From  the  axis  of  tninnions  to  base  line,  more  or  less 05 

In  the  length  of  chamber,  more  or  less 10 

C  above  axis  of  the  bore 00 

In  the  position  of  the  axis  of  the  trunnions..  I  ,   .  .      »  ..     , 

I  below  axis  of  the  bore 20 

In  the  length  of  trunnions,  more  or  less .05 

Diameter  of  trunnions,  less 0.25 

In  the  same  gun,  no  variations  to  be  tolerated  in  the  position  of  the  trunnions,  or  in  their  alignment. 

diameter  more 0.025 


In  the  vent..  -. 

do.      less .000 

(  more 10 

In  lock  piece  any  dimensions  ! 

Variation  of  position  of  exterior  orifice  of  vent 05 

Idem  of  interior  do.  do 20 

•  in  the  bore  or  vent 00 

on  exterior  surface  of  reinforces,  where  turned  or  planed .10 


elsewhere,  where  turned  or  planed .25 

on  trunnions,  within  one  inch  of  rimbases .10 

.  on  trunnions,  oNcwlirrc £5 


Depth  of  cavities . . 


Enlargement  or  indentation  of  bore  By  proof,  not  to  exceed 02 

The  measures  are  to  be  taken  by  scales  corresponding  with  the  standard  measures  of  the 
United  States. 

If  two  or  more  cavities  should  be  near  each  other  on  the  exterior,  the  gun  may  be  rejected, 
though  the  cavities  should  be  of  less  depth  than  tolerated  in  the  table. 

If  the  trunnions  are  placed  within  the  limits  of  toleration,  the  preponderance  must  not 
vary  more  than  5  per  cent.,  more  or  less,  from  that  fixed  in  the  contract. 


30 


POWDER-PROOF. 

The  proof  charges  shall  be  as  follows: 


Calibre  and  class  of  g 

tin. 

Charge  of 
powder. 

Projectile. 

Wads. 

Number   of 

fires. 

C  X  V-inch  

43,  000  Ibs. 

Pounds. 
56 

SaboUi'd" 

04* 

<*• 

Sbett- 

Xl-inch  

16,000  Ibs. 

j 

w 

""   (.15 

Shell  

10 

s 

12  500  Ibs 

f!8 

Solid  shot 

i 

~< 

U2 

Shell  

10 

J3 

9  000  Ibs 

1 

UO 

Shell  

10 

8-inch  of  63  cwt.,  or  

7,000  Ibs. 

Shot  

I 

^  UO 

Shell  

10 

.8-inch  of  55  cwt.,  or  

6,000  Ibs. 

fio 

rivX.    »   (.v-j^    00.                        \ 

\8 

Shell  

10 

[  130-pdr.  of  —  cwt.,  or  

16,  000  Ibs. 

30 

1  shot 

Gromet 

10 

64-pdr.  of  106  cwt.,  or  

12,000  Ibs. 

20 

do 

do 

10 

CO 

6,400  Ibs 

15 

do 

do 

10 

?J 

32-pdr.  of  51  cwt.,  or  

5,  700  Ibs. 

13 

....do  

....do  

10 

"o 

32-pdr.  of  42  cwt.,  or  

4,  700  Ibs. 

10 

do  

do  

10 

02 

32-pdr  of  33  cwt    or 

3,600  Ibs. 

10 

do 

do 

10 

i,  32-pdr  of  27  cwt.,  or  

3,000  Ibs. 

9 

..  do  

do  

10 

2 

H 

11 

ID 

The  cannon  powder  for  proof  shall  be  of  not  less  than  1,500  feet  initial  velocity,  as 
determined  by  the  gun  pendulum  at  the  Ordnance  yard,  Washington. 

It  shall  be  filled  in  service  cylinders,  and  well  settled. 

For  chambered  pieces  the  increased  charges  should  fill  the  chamber  and  necessary  portion 
of  the  bore. 

The  projectiles  shall  be  of  full  weight,  and  not  below  the  mean  gauge;  the  shell  shall  be 
filled  with  a  mixture  of  sand  and  ashes  to  bring  them  up  to  the  proper  weight  of  the  filled  shell. 

Sabots  for  the  shell  and  a  gromet  wad  over  the  shot. 

The  gun  should  be  fired  on  skids  or  a  proving  carriage,  to  test  the  trunnions. 

If  five  per  cent,  out  of  any  lot  offered  for  ordinary  proof  under  a  contract  shall  fail  to 
sustain  it,  the  whole  may  be  rejected,  as  may  be  stipulated  in  the  contract. 

WATER-PROOF. 

The  pressure  to  be  applied  in  the  water-proof  will  be  two  atmospheres,  or  thirty  pounds 
to  the  square  inch. 

The  penetration  of  water  in  this  proof  through  the  metal  of  the  piece,  in  any  place,  will 
cause  the  rejection  of  the  gun;  and  if,  on  examination  after  the  water-proof,  there  shall  be  any 
defects  indicated  by  weeping  or  dampness  in  the  bore,  the  gun  shall  be  rejected. 

The  water-proof  is  alone  to  be  depended  on  to  detect  minute  clusters  of  cavities  in  the 
bore,  which,  for  this  purpose,  should  be  perfectly  dry,  and  examined  by  sunlight.  All  inspec- 


*  .Modified  by  Bureau  Order  of  OctT  3'!  L8G3,  to  - 


31 

tions,  consequently,  should  take  place  in  fair  weather,  and  when  the  temperature  is  above  the 
freezing  point. 

MARKING  GDN8. 

Guns  for  the  naval  service,  received  by  authority  of  the  Bureau  of  Ordnance,  are  to  be 
marked  in  the  following  manner,  viz: 

On  the  cylinder,  in  the  line  of  sight  near  the  sight  mass,  all  accepted  guns  arc  to  have 
stamped  an  anchor  tb»«  inches  long. 

Drawings  of  these  stamps  will  be  furnished  by  the  Bureau  of  Ordnance. 

On  the  base  ring  or  line,  the  initials  of  the  foundry,  the  register  number,  and  the  weight  of 
gun  in  pounds. 

On  the  right  trunnion,  the  calibre  and  year  of  fabrication. 

On  the  left  trunnion,  the  letter  P.  and  the  initials  of  the  inspecting  officer;  all  the  above  in 
one-inch  letters. 

On  the  upper  jaw  of  the  cascalle,  the  preponderance  in  pounds  to  be  stamped  lightly  with 
half-inch  figures. 

On  the  end  of  the  upper  jaw,  the  cascable  block  and  head  of  the  pin,  the  foundry  number 
in  quarter-inch  figures. 

The  foundry  number  is  also  to  be  marked  on  the  right  rimbase. 

Guns  rejected  for  imperfections  of  any  kind  will  have  the  letter  C  stamped  on  the  anchor, 
so  as  to  partially  obliterate  it. 

The  founders  are  to  be  dissuaded  from  selling  such  guns  to  other  parties,  and  required 
to  break  them  up. 

Guns  rejected  for  such  defects  as  render  them  dangerous  to  those  who  fire  them  should  be 
irreparably  mutilated,  with  the  consent  of  the  founder. 


OluOJ    i"  1"  '"• 

Mivj;tll-lli:i!t.H. 


X..I.-  -  On  .ill  .i|.|.n.\rd  Nii\;i]    duns    HM- 

:.l:illl|lf(l    nil  tin-  1-ylilliliT   lir:ir  tin-    n1 
Ill    tll<-      I  .....     Ill'    Sl'jlll 

_  When  tin-  (Inn  is    f.,  mil-mill',  I    lli.     I.  -Mi-r   "'  istn  I 


32 

EXTREME  PROOF  OF  TRIAL  GUNS. 

The  extreme  proof  of  guns  intended  for  trial  of  metal,  subject  to  such  modifications  by 
the  Bureau  as  future  experience  may  dictate,  will  be  conducted  as  follows: 

A  suitable  "butt"  shall  be  erected  to  arrest  the  flight  of  the  projectile  used  in  proof,  and 
to  admit  of  their  easy  recovery,  and  a  bomb-proof,  readily  accessible,  for  the  protection  of  the 
firing  party. 

When  practicable  the  "butt"  should  be  made  thick  enough  to  allow  the  shot  to  just  pass 
through,  and  be  stopped  by  another  beyond  it,  without  penetrating  the  latter;  this  is,  for 
Xl-inch,  about  12  feet. 

With  care,  it  is  estimated  that  130  shells  may  be  fired  1,000  times,  at  the  rate  of  one 
hundred  rounds  per  day. 

After  undergoing  the  ordinary  proof  established  for  its  calibre  and  class,  the  gun  selected 
for  extreme  proof  shall  be  subjected  to  at  least  1,000  rounds  with  service  charges. 

It  may  be  fired  from  the  skids,  or  suspended,  as  the  Bureau  may  direct. 

During  the  trial  the  gun  shall  be  frequently  and  critically  examined  inside  and  out  for 
cracks  or  defects,  especially  about  the  interior  orifice  of  the  vent,  of  which  impressions  are  to  be 
taken  in  wax  at  regular  intervals  in  the  manner  prescribed  on  page  26,  or  in  such  other  manner 
as  the  Bureau  may  direct.  If  they  show  that  the  vent  is  corroded  in  furrows,  and  enlarged 
considerably  in  diameter  at  its  junction  with  the  bore,  a  permanent  impression  is  to  be  taken 
in  lead  to  show  the  conical  enlargement.  The  following  manner,  practiced  at  the  Experimental 
Battery  at  Washington,  is  recommended: 

IMPLEMENTS   REQUIRED. 

1.  A  soft  wire  about  0.07  in.  diameter,  and  3  or  4  fathoms  long. 

2.  A  lever  about  twice  the  length  of  the  bore,  and  about  3  inches  in  diameter,  and  shod 
to  suit  the  curve  of  the  bore  nearly. 

3.  A  small  button  of  soft  lead,  judged  to  be  of  sufficient  size  to  fill  the  vent  at  least  one 
inch  from  the  bore.     This  is  to  be  pierced  lengthwise  to  receive  the  wire. 

TO  TAKE   THE  IMPRESSION. 

Shove  the  wire  through  the  vent;  let  it  pass  along  the  bore  and  out 'at  the  muzzle;  put  it 
through  the  leaden  button  and  tie  a  knot  at  the  end.  Draw  the  wire  back  through  the  vent 
until  the  leaden  button  is  introduced  firmly  into  the  inner  orifice. 

Apply  the  lever,  making  its  shoe  bear  on  the  button,  and  force  it  well  in  by  repeated 
blows,  the  muzzle  being  the  fulcrum.  This  done,  disengage  the  button  by  pushing  in  the 
priming-wire. 

In  taking  impressions  of  the  vent  and  cracks,  each  button  in  turn  is  used  as  a  pattern  for 
moulding  its  succsssor,  allowing  for  the  progressive  enlargement  of  the  vent,  or  the  cracks 
emanating  from  it.  When  the  crack  shows  itself,  the  head  of  the  button  should  be  so  enlarged 
as  to  include  it. 


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33 

They  examinations  should  take  place  after  every  twenty  fires,  at  least,  and  more  frequently 
any  unusual  enlargement  of  the  vent  or  extension  of  cracks  shall  be  developed  and 
indicate  its  speedy  destruction. 

Before  each  examination  the  bore  of  tho  gun  is  to  be  carefully  washed  and  dried. 

In  recording  the  measurements  of  the  bore  in  extreme  proof  and  after  service,  distinguish 
between  "indentation,"  which  is  the  depression  at  the  " seat  of  the  shot, "  which  is  always 
below,  and  the  "wear  of  the  bore,"  which  is  generally  above,  and  increase  of  bore  or  "en- 
largement" from  any  other  cause. 

When  from  the  appearance  of  tho  bore  at  the  interior  orifice  of  the  vent,  and  especially 
when  a  crack  or  cracks  appear  to  be  extending  rapidly,  the  vent  so  enlarged  may  be  filled 
with  melted  tin,  zinc,  or  Babbitt  metal;  a  tight-fitting  sponge  head  being  pushed  to  the  bottom 
of  the  chamber  to  close  the  interior  orifice,  and  the  other  vent  be  drilled  through  for  the  pur- 
pose of  continuing  the  firing. 

The  precise  time  at  which  this  is  to  be  done  will  vary,  according  to  circumstances;  such 
as  quality  of  metal,  charge,  and  elevation. 

The  endurance  of  a  gun  with  service  charges  may  be  surely  predicted  by  observation  of 
the  progressive  wear  of  the  interior  orifice  of  the  vent. 

There  are  certain  general  forms  in  which  this  enlargement  takes  place.  They  may  be 
classed  as  triangular,  lozenge,  quadrilateral,  star,  circular,  and  elliptic.  (See  plate.) 

With  the  ordinary  central  vent,  when  subjected  to  a  rapid,  continuous  fire,  the  enlarge- 
ment usually  takes  the  form  of  an  isosceles  triangle,  the  apex  of  one  of  the  angles  towards  the 
muzzle,  and  tlu3  other  two  perpendicular  to  it. 

With  the  lateral  vent  of  the  Dahlgren  system  it  usually  takes  the  lozenge  form,  the  cracks 
extending  from  the  opposite  angles  lengthwise  of  the  bore. 

With  those  rifled  cannon  in  which  the  vent  is  bouched,  the  cracks  appear  around  the 
bouching,  and  although  the  bouching  preserves  the  vent,  yet  the  formation  of  fissures  around 
the  enlarged  orifice  when  once  commenced  causes  a  greater  tendency  to  rupture.  With  the 
vent  not  bouched,  the  wear  in  rifled  cannon  is  about  double  that  of  the  smooth  bore. 

So  long  as  the  wear  of  the  vent  is  regular  and  without  cracks,  a  mere  enlargement  is  not 
indicative  of  danger  ;  but  when  it  reaches  a  diameter  of  four-tenths  (.4)  of  an  inch  the  vent 
should  be  closed  and  a  new  one  opened. 

A  gun  of  large  calibre  should  not  in  service  be  expected  to  endure  more  than  400  or  500 
rounds  before  it  will  be  necessary  to  open  the  new  vent,  which,  however,  will  be  of  no  advan- 
tage, unless  the  old  one  be  closed  at  its  interior  orifice,  on  which  the  gases  would  otherwise 
continue  to  act  as  a  wedge. 

The  first  distinct  appearance  of  the  cracks,  as  shown  by  the  button,  is  the  proper  limit. 

After   the  gun  bursts,  make  a  sketch  or  draft  showing  lines   of  fracture,    and  reserve 
specimens  to  be  sent  to  the  Ordnance  yard  at  Washington  for  trial  of  density  and   tensile 
strength  ;  and  if  practicable,  a  photograph  should  be  taken. 
5 


34 

PREPARATION  OP  GUNS  FOR  SERVICE.  • 

After  the  guns  have  been  received  at  the  navy  yards  it  is  necessary  to  adjust  the  sights, 
and,  in  the  guns  of  the  Dahlgren  pattern,  cut  the  screw  hole  in  the  cascable. 

CUTTINJ}   THE   SCREW   HOLE. 

The  boring  and  screw-cutting  machine  is  a  convenient  portable  hand  drill-press,  the  use 
of  which  is  readily  understood  by  any  machinist. 

The  gun  being  carefully  levelled  and  the  trunnions  placed  horizontal,  the  position  of  the 
centre  of  the  screw  hole,  which  in  the  guns  of  the  Dahlgren  pattern  is  tangent  to  the  radius 
of  the  breech,  is  marked  on  the  neck  of  the  cascable  with  a  centre  punch. 

The  machine  is  placed  on  the  cascable,  the  boring  shaft  inserted  in  the  hollow  leading  bar, 
and  its  movable  centre  placed  on  the  mark.  The  instrument  is  then  set  vertical,  by  a  spirit 
level  on  the  cogged  driving  wheel  and  the  four  pairs  of  set  screws  on  the  clamp-head  embra- 
cing the  cascable. 

The  centre  is  then  removed  and  a  drill  inserted  in  the  lower  extremity  of  the  boring  shaft, 
which,  being  held  firmly  by  a  shoulder  and  turned  by  a  four-armed  wrench,  while  pressed  up 
to  the  metal  by  slowly  turning  the  cogged  driving  wheel,  cuts  the  hole.  This  is  successively 
enlarged,  by  two  or  more  counterbits,  to  the  size  of  the  body  of  the  screw. 

The  cutter  is  then  inserted  in  the  leading  bar,  and  the  thread  cut. 

ADJUSTMENT   OF   THE   SIGHTS. 

The  bore  having  been  thoroughly  cleaned,  the  axis  is  levelled  by  a  spirit  level;  this  may 
be  very  conveniently  done  by  the  aid  of  the  levelling  bar.  The  axis  of  the  trunnions  is  to  be 
placed  horizontal,  either  by  placing  a  small  level  on  the  trunnions,  or,  as  more  exact,  by  using 
the  trunnion  square.  If  the  trunnion  square  is  used  it  will  be  proper  to  verify  the  position  of 
the  line  of  sight,  which  is  frequently  incorrectly  placed  at  the  foundries. 

The  breech  sight  is  then  to  be  adjusted. 

A  brass  head  or  tompion,  fitted  with  a  vertical  arm,  on  which  there  is  a  ledge  for  a  spirit 
level,  is  then  introduced  into  the  bore,  and  the  arm  placed  vertical  by  the  spirit  level  and  a 
tangent  screw. 

The  arm  is  pierced  on  its  centre  line  with  two  holes — one  at  the  height  of  the  prescribed 
diameter  of  the  muzzle,  the  other  nt  a  height  equal  to  the  proper  distance  of  the  bottom  of  the 
sight  notch  from  the  axis  of  the  bore.  A  waxed  thread  or  fine  wire  being  stretched  from  the 
upper  hole  to  the  centre  of  the  sight  notch  will  coincide  with  the  line  of  sight  traced  on  the 
swell  of  the  muzzle,  the  top  of  the  reinforce  sight  mass,  and  the  base  line,  if  they  are  correctly 
placed.  It  will  also  be  parallel  to  the  axis  of  the  bore  if  the  adjustment  of  the  breech  sight 
is  exact,  and  the  top  of  the  reinforce  sight  is  made  to  coincide  with  it. 

This  is,  however,  seldom  the  case,  and  after  the  adjustment  of  the  reinforce  sight  it  is 
necessary  to  verify  it. 

This  is  done  by  the  levelling  bar — a  square  steel  bar  with  parallel  faces,  somewhat  longer 


3 

o 

20 


07 

•J 


I 


m 
o 


01 
co 


m 
co 


O 

3 
O 


o 


o 
o 


. 


0 
• 


~> 


35 

than  the  distance  between  the  sights,  the  rear  end  of  which  is  bevelled  at  CO0,  (the  angle  at 
which  the  sight  is  placed*) 

The  outfcr  end  of  this  bar  is  placed  on  the  reinforce  sight,  which  has  been  previously 
adjusted  to  the  proper  height,  and  the  bevelled  end  in  contact  with  the  outer  face  of  the  sight 
bar.  The  bar  is  then  levelled  by  two  screws  placed  near  the  inner  end,  and  a  spirit  level  on 

its  npper  surface. 

If  then  the  bottom  of  the  sight  notch  coincides  with  the  bottom  of  the  bar,  the  line  of 

eight  is  parallel  to  the  axis;  otherwise,  the  reinforce  sight  or  the  sight  bar  must  be  lowered 
until  coincidence  is  obtained. 

A  centre  line  on  the  bar  verifies  the  coincidence  of  the  line  of  sight,  and  also  the  motion 
of  the  sight  bar  in  the  vertical  plane.  The  bevel  verifies  the  angle  of  the  bar,  and  the  dis- 
tance between  the  outer  faces  of  the  sight  notch  and  of  the  reinforce  sight  being  also  marked 
on  the  levelling  bar,  verifies  this  adjustment. 

Another  method  is  sometimes  and  more  advantageously  used  in  adjusting  the  sights  of 
puns  which  have  not  been  turned. 

Twoyfron  or  wooden  discs  are  turned  to  the  exact  diameter  of  the  bore, 

nxi  twanr  three  feet  longer  than  the  boreX  One  of  the  discs  ik  placed  near  *ne  hflttom  ui  yuo       ^      t 
borevfeie  other  just  w/ithni  the  muzzle.  /On \be  part  proiecting\eyond  tire  muzzlev there/is  a    j^     ,_£> 
double  ffHuare,  each/arm  of^hich  is  divided  inbo  equal>parts  and  nayversed  by  a  fine* 

The  ffauaro  being  set  vertical  by  a  spirit  level  or/plumb  line,  aruLii  waxed  thread/oN:  wire 
stretched  auit/from  the  outerVarm  through  the/Wit,  cutting  equalVivisions  on/eacbVind 
passing  through  the  centre  of/tneNelit,  it  is  evident  tba\a  line  ofynght  isN^btaine^r  through/The 
centre  of  nfetal\nd  parallol/U)  the  aicis  of  the/bore. 

Thijr  method  najs  the/advantage  of  adjusting  the  sights/In  any  plane  parallel  to  the  axis, 
as  in  the  case  of  the  aide  sights  of  rifled  and  other  cannon.  ,-* 

• 

ADJUSTMENT   OF  THE   SIDE   SIGHTS. 

The  gun  having  been  levelled,  and  the  trunnions  placed  horizontal,  a  centre  line  is  to  be 
drawn  on  the  top  of  the  left  (or  right)  rimbase. 

The  support  for  the  sight  is  then  to  be  fitted  to  the  breech,  at  the  distance  from  this  line 
marked  on  the  pattern  sight  for  its  calibre,  with  the  bottom  of  the  sight  notch  in  the  bar, 
exactly  the  height  of  the  front  sight  (one  inch)  above  the  upper  surface  of  the  rimbase  ;  the 
sight  bar  perpendicular. 

It  is  advisable  to  place  a  very  thin  sheet  of  rubber  under  the  support  to  prevent  the  heads 
of  the  screws  from  being  jumped  off  by  the  vibration.  The  screws  have  the  same  thread  as 
those  for  the  present  reinforce  sight. 

After  the  breech  sight  is  adjusted  a  parallel  to  the  axis  of  the  bore  is  to  be  drawn  in  the 
usual  manner,  and  the  front  sight  screwed  in  on  the  rimbase. 

Some  trifling  adjustment  may  then  be  required  to  bring  the  height  of  the  top  of  the 
front  sight  and  the  bottom  of  the  sight  notch  parallel  to  the  axis  of  the  bore  in  both  the 
horizontal  and  vertical  planes. 


37 

REPORT.— FORM  (1.) 

NOTE. — The  Proof  Gun  is  to  be  entered  at  bead  of  each  page  In  red  ink. 


CIIAKOE  OF  FURNACE,  IN  POUNDS. 


NO. 


NO. 


38 


CHARGE  OP  FURNACE,  IN  POUNDS. 


NO. 


TOTAL  IN  POUNDS. 


NO. 


MO. 


COMBINATION  OP   METAL,  PER   CENTUM. 


FOTNACK 


FUEL. 


BLAST. 


NO. 


40 


NO. 


DATE  OP  CASTING. 


TIME. 


REQUIRED  TO  OBTAIN 
COMPLETE  FUSION. 


KEPT  IN  FUSION. 


OF  FILLING  MOULD. 


REMAINED  IN  OPEN 
PIT. 


NO. 


41 


rh  uwiif  •  to  Iw  nut,  showing  tlw  ciMCt  plicw  nwtrt 


MKAN  DENSITY  AND  TENSILE  STRENGTH  OF  3  SPECIMENS. 

MO. 

NO. 

AT  FODKDBT. 

AT  WAIUIKOTON. 

DKJI0TT. 

TIXtlLZ  mUWOTH. 

DIUMTT. 

••ft 

Con. 

BMd. 

Core. 

HMd. 

Con. 

HMd. 

Con. 

» 

• 

• 

% 

42 


EXCESS  OF  ROUGH    OVER  FINISHED 

GUN  HEADS. 

DIMENSIONS. 

NO. 

--  at  Muz- 
'ace. 

"3 

s 

"2 
00  £ 

Si 

"S 
t 
v  f: 

3 

ea     . 

00      £ 

8  at  Breech 
y  Under. 

LENGTH. 

DIAMETER. 

TIME  OF  BORING. 

TIME  OF  TURN- 
ING. 

NO. 

I1 

M 

|J 

W 

CJ 

S  a 
w 

a 

w 

0 

So 
1- 

w  g 

«j 

Inches. 

Inches. 

luchee. 

"*1 

• 

43 


METAL  WORKED. 


NO. 


AT  FOURDKT. 


AT  WASHMOTOK. 


CAVITIES,  Ac. 


NO. 


44 


APPEARANCE  AT  FOUNDRY  OP- 


NO. 


NO. 


FRACTURE  OF  CORE. 


CORE. 


BORE.  EXTERIOR  SURFACE. 


NO. 

WEIGHT  OP 
GUN. 

PREPONDER- 
ANCE. 

DISTANCE  FROM 
BASE-RING  TO  CEN- 
TRE OF  TRUNNIONS. 

MAXIMUM  INDEN- 
TATION BY  POW- 
DER PROOF. 

DIAMETER  OF  BORE  BY 
8TAROAUUE,  AFTER  PROOF. 

HO. 

POD  NIX. 

POUNDS. 

INGRES. 

IOOOTHS  or  AN  INCH.         GREAT*  »r. 

LlAlT. 

Rfcbt. 

Left. 

• 

* 

46 


NO. 


NAME  OF  INSPECTOR. 


ARE  THE  INSPECTOR'S  MEASURE- 
MENTS WITHIN  REGULATION 
LIMITS  J 


NO. 


47 


HO. 


REGISTER. 
NO. 


REMARKS. 


NO. 


48 


REPORT.— (FORMS.) 
Dimensions  of guns  cast  at  the Foundry  of ,  18 


CLASS. 

LENGTHS  FROM  A,  THE  BASE,  TO  . 

inch. 
Ibs. 

B. 

C. 

D. 

e. 

E. 

F. 

G. 

H. 

I. 

K. 

L. 

Left. 

Right. 

Prescribed  dimensions  - 

• 

Foundry  No. 

DIAMETER  AT  . 

A. 

C. 

D. 

E. 

F. 

G. 

H. 

I. 

K. 

L. 

Gun. 

Rimbases. 

Prescribed  dimensions. 

• 

Foundry  No. 

• 

• 

* 

MISCELLANEOUS. 

LENGTHS. 

Diameter  of 
bore. 

°! 

WEIGHT  OF  GUN. 

Preponder- 
ance at  base. 

0 

fe4 
fl 

o 

Int.  of  vent, 
dist'ce  from 
a. 

Int.  of  vent 
dist'ce  from 
axis. 

Bore, 
a  c. 

Chamber, 
ab. 

Lbs. 

Prescribed  dimensions  - 

Foundry  No. 

\ 


"y  > 


49 


R  E  I'O  R  T  .—(FORM  2)— Continued. 


X. 

X. 

O. 

(REK  DIAGRAM.) 

P 

LKHOTH  or  TRi-.i- 

noM. 

KKMAKKN. 

Left. 

Rl«bt 

- 

C'.vIlndiT  gnge  dMcciub. 

(SEE  DIAGRAM.) 

U. 

N. 

O. 

p. 

TKUXMOXS. 

RIMBA8U. 

Tmnnlonn 
below  *xi> 

Left. 

lilt-Ill. 

Left. 

Right 

» 

CHAROEI  or  Povt- 
Dot.  tu. 

Powder,   bjr   whom 
Kurt-.  mxld.tr  of 
mUBftctan. 

IMTUI.     TELOriTT 

or  rowoiK,  FKKT. 

WEIGHT  or  PIMM- 
TILE.  LBS. 

• 

50 

REPORT.— (FORM  3.) 

The  excess  over  prescribed  diameter  of  bore  before  and  after  proof,  as  found  by  the  star  gauge,  at  different 
der  (  inches  from  face)  to  seat  of  shot;  thence  at  every  *«•»•  inch**  to  trunnions,  ( 

searched  for  and  recorded,  with  its  distance  from  face ;   thus — 


Calibre  and  No.  of  Gun. 

inch   •>  B.  P. 

Foundry  No.                 )  A.  P. 

inch    }  B.  P. 
Foundry  No.                 )  A.  P. 

inch   )  B.  P. 

Foundry  No.                 S  A.  P. 

& 

inch   IB.  P. 
Fonnflry  No.                 )  A.  P. 

• 

inch   IB.  P. 
Foundry  No.                  J  A.  P. 

inch  }B.  P. 
Foundry  No.                 J  A.  P. 

51 


REPORT.— (FORM  3— Continued. 


distance*  from  the  muzzle,  to  lie  taken  at  every  J  inch  from  the  bottom  of  the  cylin- 

inches  from  the  face  ;)  thence  every  five  inches.     The  greatest  enlargement  to  be      1 

ii 

ih 

!i 

iz  S     i        fc 

.! 

m  i  s 

- 

• 

